Description:
Nutrient water preparation systems of the steam boilers of the average and high pressure ("Roof boiler houses" and mini-CHP) for heat supply of buildings or city residential complexes (CTP) (in a combination of developed nanofiltration systems with reverse osmosis systems).
A. G. Perevov, Prof., Dr. Tehn. Sciences, Department of Water Supply MGSU
A. P. Andrianov, Cand. tehn Sciences, Department of Water Supply MGSU
D. V. Swords
V. V. Kondratyev, engineer, Department of Water supply MGSU
Modern rates of development of construction technologies do not always keep up with the development of water treatment technologies used for the sanitary equipment of modern buildings. The use of clearly obsolete technologies often creates interference to construction. For example, the need to create water purge stations in buildings makes it solve issues of placement, installation and operation (service). Therefore, not only the quality of water, but also the dimensions of the structures, the cost of installation and operation, which take into account the volume of wastewater and water to their own needs, depend on the chosen technology.
Traditional technologies using pressure filters with sand, coal and ion exchange resins are sufficiently "bulky", require costs when operating (replacing downloads or regeneration them), form drabs when washing them and regeneration.
Improvement of nanofiltration systems allows you to create equipment with minimal weight and dimensions, simplicity of installation and "increasing" power, minimal maintenance costs, lack of reagents and consumables.
The modern environmental situation contributes to wider use of membrane systems. This is primarily due to the tightened quality requirements. drinking water - content of chlororganic compounds, pathogenic bacteria, fluorides, nitrates, strontium ions, etc. Modern membranes demonstrate indisputable efficacy and versatility in water purification from different species Pollution. The second main feature of modern membrane technologies is their "environmental" purity - the absence of reagents consumed and, accordingly, hazardous to the environment of discharges and precipitation, creating the problem of their disposal. The introduction of fees for using tap water and for discharges into sewage causes water treatment systems that consume the minimum amount of water and not having discharges. Modern development of water treatment systems using membrane technologies allow you to supply engineering systems High-quality water, thereby ensuring the reliability and quality of their work.
The membrane processes of ultrafiltration and nanofiltrations have long attracted the attention of water supply professionals due to their "universality" - the possibilities of simultaneous removal of a number of pollution of different nature: biological (bacteria and viruses), organic (humic acids, etc.), colloidal, weighted, as well as soluble in ion form. Differences in membrane processes consist in the level of water purification (skipping into the purified water of certain contaminants), depending on the size of the pores of the membranes.
The technology of nanofiltration is known for quite a long time and is already beginning to be used in drinking water supply due to the effective decrease in the content of organic compounds (chroma, volatile chloroorganic compounds) and iron, as well as stiffness.
The nanofiltration method is already widely used to clean surface and groundwater, including on major urban structures (for example, at the stations in Paris - 6000 m 3 / h and the Netherlands).
However, until now, the method of nanofiltration is considered as a kind of reverse osmosis method with all its disadvantages: the need for a thorough preservice to prevent the formation of calcium carbonate sediments and precipitation of organic and colloidal substances; high operating costs associated with the dispensing of preservation reagents, using detergent solutions and a high cost of replacing membrane modules; Traditional membrane modules of the type "roll", not distinguished by high reliability. High reagent expenses and other operating costs cause specialists while skeptically refer to the use of nanofiltration to prepare high-quality water on large water treatment plants despite indisputable efficiency in comparison with "classic" coagulation and oxidative and sorption technologies.
Currently, the extensive scale of industrial implementation has the method of ultrafiltration, which is used mainly on the treatment facilities of urban water pipes: from December 2006 - in Moscow in the south-western station (as well as on the water-receiving stations of Paris, London, Amsterdam, Singapore, in a number of cities USA, Canada).
However, the use of ultrafiltration membranes (with a pore size of 0.01-0.1 μm) has a very limited scope (reduction of colloidal particles and bacteria) and is not versatile when cleaning waters of various composition. Therefore, in water purification schemes, ultrafiltration is used in combination with other technologies (coagulative and oxidative-sorption). The main advantages of ultrafiltration is very high specific performance (more than 100 l / m 2 h compared with 35-40 l / m 2 h in nanofiltration) and the ability to wash the membrane reverse current to remove with membranes of contamination.
Thus, the purpose of the work was to study the possibility of overcoming the basic shortcomings of the method of nanofiltration and the creation of technology combining the effectiveness of nanofiltration and simplicity of ultrafiltration.
Prerequisites for creating such technology have been ripe for a long time. Methods for cleaning surface waters are known using nanofiltration of major European firms NORIT (Netherlands) and PCI (UK) using special tubular structures, allowing to reduce sedimentation and conduct hydraulic flushing with pressure discharge for "breakdown" of contaminants from the membrane surface. However, tubular designs have a very small specific surface area of \u200b\u200bmembranes and significantly increase the volume of installations and their power consumption, which ultimately is expressed in high values \u200b\u200bof specific capital and operating costs.
Modern membrane apparatuses of rolling construction have a big advantage over the tubular form membranes in the form of a hollow fiber used in modern ultrafiltration installations - this density of the "membrane packaging" or a high specific surface area of \u200b\u200bthe membrane per unit volume of the device. With the same sizes of "standard" membrane modules (diameter 200 mm, length 1000 mm), the total membrane surface in the ultrafiltration module is 18-20 m 2, and in nanofiltration 35-40 m 2. Moreover, the cost of producing a rolled module with flat membranes is significantly (50-60%) cheaper than half-fiber. Therefore, the main focus of the work was the improvement of the rolled construction in order to improve the reliability of work and "sustainability" to pollution. The imperfection of the rolled element is associated with the presence of a grid-separator in it (Fig. 1), which is a "trap" for contamination. Therefore, the creation of devices with the "open" channel without a biased grid avoids the accumulation of pollution during operation and to ensure the possibility of hydraulic flushing with pressure discharge. The selection of optimal nanofiltration membranes and the development of technology for the production of membrane modules of various sizes made it possible to create non-reagent technologies for a number of water purification. The absence of reagents in the scheme is provided, on the one hand, the high efficiency of membranes in relation to the detention of dissolved impurities, on the other, the constant removal of contamination from the surface of the membrane due to automated hydraulic flushes and maintaining the filtering surface of the purity membrane.
Due to the developed structures of the devices and automated flushes, technologies have been created that allow cleaning water with a high content of suspended substances, iron, stiffness, chroma. Depending on the composition of the purified water (mainly the content of organic substances of various nature), a membrane brand is selected with the most appropriate selective properties. Different types of membranes were tested for cleaning surface and groundwater, but new developments of cellulose acetate membranes with special stabilizing additives demonstrated the greatest efficiency. Due to the hydrophilic surface of the membrane, iron ions dissolved organic substances are extremely efficiently delayed. In addition, due to the surface properties, a number of colloid and organic compounds are worse than the acetate membranes than composite. The provisions described above were proved by comprehensive research described in the accompanying publications. There are no analogues to the developed devices and membranes, both in domestic and foreign firms. The technology for obtaining membranes and the production of rolled elements with the "open" channel also represents the know-how and is not disclosed in detail. Attempts to improve the channels of roll elements were carried out by a number of authors for a long time, but the results were not brought to a wide industrial implementation due to the complexity of the technology. In this paper, the manufacturing technology has been used, previously outlined and patented, but thanks to the joint actions of the authors improved and under patenting.
Developed nanofiltration devices are competitive in cost, performance and washing regime with ultrafiltration machines, being much more efficient to private properties. In fig. 2 shows the dependence of the performance of the "standard" sizes from time when cleaning surface water from the river.
Due to the loss of performance in the formation of precipitation and irreversible clogging of pores by suspended particles, the average productivity of ultrafiltration membranes is 40-50% less "passport", differing at 30-40% of the performance of the apparatus with nanofiltration membranes.
Water in centralized water pipes often contain weighted colloidal substances (for example, iron hydroxide), as well as bacteria due to secondary pollution of water in the waterways. In some cases, an increased content of chlorine-organic substances is observed (during floods). Traditionally, mechanical pressure filters are used to remove suspended substances, and to reduce the content of organic substances and odors - filters with sorption loading.
The main disadvantages of this approach are: the use of sufficiently bulky filters (usually imported from fiberglass with a dimode of 0.75-1.2 m and a height of more than 2 m); difficulties when installing filters in existing rooms; complexity of service and replacement of downloads; Quite rapid depletion of the sorption container coal and the need to replace it.
Recently, instead of mechanical filters, ultrafiltration installations are used, allowing to ensure a deeper removal of iron colloids, bacteria and viruses from water. In addition, membrane installations are compact, have significantly smaller weight and volume compared with mechanical filters, which is especially important when using and accommodating in urban buildings. However, the use of sorption filters in urban buildings requires, due to limited sorption capacity of downloads, sufficiently high costs for maintenance of such installations.
The use of nanofiltration installations allows you to solve the problem of removing organic contaminants from water water Without use of sorption filters and with minimal operating costs.
Calculations and studies show that the removal by the method of nanofiltration of most (over 90%) of organic contaminants allows to extend the resource of sorption filters 10-20 times or accordingly reduce their volume, limiting the use of cartridge filters only in case of presence in water odors during floods or emergencies in water on the water source. In addition, nanofiltration membranes are partially removed from water rigidity and alkalinity, making water suitable for heat supply and hot water supply systems, eliminating the customer from the need to use softeners and additional consumables (tableted salts).
Modern customers in urban sites often form additional requirements for water quality, significantly more stringent than the requirements of existing WHO and Sanpine standards, which is caused by the presence of "special" consumers - a polyclinic, medical wellness centers, catering enterprises, etc. in the buildings.
So, for example, when designing the zezoscope of the federation of the federation, the designers "collided" with the requirements for the content of iron -0.05 mg / l, GSS (halogen-containing compounds) -10 μg / l (against WHO standards: 0.3 mg / l and 200 μg / l, respectively). Similar requirements were decisive in the selection of nanofiltration systems for water supply of central rear customs and Polyclinics of the FSBV Moscow in 2002 (Fig. 3, 4).
In this paper, studies were conducted comparing the effectiveness of the decrease in the oxidizing water and the content of dissolved organic substances using ultrafiltration systems with sorption treatment and nanofiltration systems. The quality of purified water was evaluated in oxidizing indicators.
Water quality is generalized as evaluated by the nature of the light pulp curves, where certain wavelengths correspond to the molecular weight and nature of organic substances.
In fig. 5 shows the curves of the light absorption of tap water transmitted through nanofiltration membranes 4 and the filter with a load from coal 2 and 3. The use of nanofiltration membranes 4 allows you to get water with low oxidizing rates. In addition, the use of sorption filters after nanofiltration only to remove the smell, their resource increases many times. The results of the resource testing of the sorption filter (definition of its sorption capacity) are shown in Fig. 6.
The economic effect of applying the technology of nanofiltration is determined by the reduction in the cost of maintenance of appliances.
The current state of urban construction requires solving problems of supplying buildings not only quality drinking watersatisfying the requirements of SanPiN, but in some cases, water for special technological needs:
feeding the contours of the heat seafood and heating;
feeding contours of irrigate and evaporators of air conditioning systems;
Fitting steam boilers "roof boiler houses" for heat supply systems.
Depending on the requirements for the quality of the prepared water in nanofiltration systems, various types of membranes with different selectivity indicators are used (skewing ability). When using membrane installations for the needs of the heat seafood and hot water supply, the ki carbonate index of purified water must satisfy the following conditions:
Ki \u003d [sa +2] · ≤ 2-5,
where, the values \u200b\u200bof calcium concentrations and alkalinity, expressed in mM-eq / l.
To ensure such requirements, nanofiltration membranes are ideally suited to the developed membrane elements with an "open channel", eliminating the formation of congestion zones in the devices and the formation of calcium carbonate in them, sharply reduces the operation time of the device.
If it is necessary to obtain nutrient water for steam boilers and contours of air conditioning systems, water is required with rigidity values \u200b\u200bat the level of 0.01-0.02 mg-eq / l. Traditionally, for obtaining deeply softened water uses two-stage Na-cation systems or (at present) instead of the first Na-cation setting - installation of reverse osmosis. In fact, in another case, the deep softening scheme requires high operating costs (on a tablet salt, an inhibitor, detergent solutions, frequent service) and solving the problems of regenerative solutions. When using the developments presented in the work, the diagrams of two-stage softening were created (using at the stage of membrane nanofiltration machines) and reverse osmosis devices on stage II (Fig. 7).
Such schemes make it possible to avoid the use of reagents during their operation and provide long-term (over 2500 hours) a period of non-stop operation. In some cases, it is advisable to use specially designed cartridges with a powdered inhibitor to increase the reliability of reverse osmosis systems.
To determine the performance characteristics of membrane diagrams using reverse osmosis and nanofiltration devices (determination of types of detergent solutions, continuous operation, etc.) A special computer program has been developed.
An example of comparing operating costs of various deep softening schemes is shown in Fig. eight.
Through the use of new types of membranes and membrane devices, the operating time is maximally increased, which leads to a decrease in the cost of maintenance maintenance (Fig. 9).
The general view of two-stage membrane systems is shown in Fig. 10.
The technologies described are used in the development:
Water purification systems for centralized water supply: surface water purification stations and an underground water purification station with a capacity of up to 10,000 m 3 / h; systems are completely unreoughtled;
Water purification systems for microdistrict and industrial and shopping complexes;
Systems of improving the quality of tap water for individual residential and office buildings;
Systems for the preparation of water feed heatpets and boilers of residential and industrial buildings;
System improvement systems of nutritious water from technical water pipelines of urban enterprises;
Nutritional water preparation systems of medium and high pressure steam boilers ("roof boilers" and mini-CHP) for heat supply of buildings or urban residential complexes (CTP) (in combination of developed nanofiltration systems with reverse osmosis systems). The developed technologies make it possible to solve the problems with the use of compact, easily mounted equipment with simple "increasing" power providing an automated round-the-clock mode of operation that does not need reagents and consumables and requiring service activities not more than after 6 months of continuous operation.
For water supply of a large (residential or hotel building), the water treatment system may consist of four membrane blocks with a total capacity of 50 m 3 / h. The dimensions of each block (with a capacity of 12 m 3 / h) are 1.5 m (depth) x 1.5 m (height) x 0.5 m (width). The overall dimensions of the station with a capacity of 50 m 3 / h are (SHHDHV) 3.5x1, 5x1.5 m. The package of each block includes: a boom pump, membrane machines, cookti cartridges with coal. Operation of the system is to carry out prophylactic flushing (1 -2 times per year) and replacing coal cartridges (1 time per year). Membrane service life is 5 years. The layout of one block is shown in Fig. 11, the general view of one block with a capacity of 12 m 3 / h is shown in Fig. 12.
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This section describes in detail the existing traditional methods of water treatment, their advantages and disadvantages, as well as modern new methods and new technologies for improving water quality in accordance with the requirements of consumers.
The main tasks of water treatment are obtaining at the output of pure safe water suitable for various needs: economic and Drinking, Technical and Industrial Water Supply with considering economic feasibility Applications of the necessary methods of water treatment, water treatment. The approach to the water purification cannot be the same everywhere. The differences are caused by the composition of water and the requirements for its quality, which differ significantly depending on the purpose of water (drinking, technical, etc.). However, there is a set of typical procedures used in water purification systems and the sequence in which these procedures are used.
Main (traditional) water treatment methods.
In the practice of water supply in the process of cleaning and processing, water is exposed lightening(exemption from suspended particles), discoloration (elimination of substances giving water color) Disinfection (The destruction of pathogenic bacteria in it). In this case, depending on the quality of the original water, in some cases, the special methods for improving water quality are additionally applied: softening water (decrease in rigidity due to the presence of calcium and magnesium salts); phosphating (for deeper water softening); desalination, desalinationwater (reducing the total mineralization of water); extermination, Defeling water (the release of water from soluble iron compounds); degasywater (removal of soluble gases from water: serovodorod. H 2 S, CO 2, O 2); deactivationwater (removal of radioactive substances from water.); neutralitywater (removal of poisonous substances from water), fluorination(add to fluoride water) or Fingering (removal of fluorine compounds); acidification or alkalization (for water stabilization). Sometimes it is necessary to eliminate the tastes and smells, prevent the corrosive action of water, etc. Those or other combinations of these processes apply depending on the category of consumers and water quality in the sources.
The quality of water in the water object and is determined by a number of indicators (physical, chemical and sanitary and bacteriological), in accordance with the purpose of water and the established quality standards . In detail about it in the next section. Comparing water quality data (obtained according to the results of analysis) with the requirements of consumers, define measures for processing it.
The problem of water purification covers issues of physical, chemical and biological changes in the processing process in order to make it suitable for drinking, i.e. cleaning and improving its natural properties.
The method of water treatment, composition and calculated parameters of wastewater treatment plants for technical water supply and calculated doses of reagents are established depending on the degree of pollution of the water object, the purpose of the water supply, station performance and local conditions, as well as on the basis of these technological research and operation of structures operating under similar conditions .
Water purification is made in several stages. Garbage and sand are removed at the preservation stage. The combination of primary and secondary purification, carried out on water treatment facilities (BB), allows you to get rid of colloidal material (organic substances). Dissolved biogenes are eliminated using the cooking. So that cleaning was complete, water treatment facilities must eliminate all categories of pollutants. For this there are many ways.
With the appropriate doctor, with high-quality equipment, the Bos can be achieved that in the end, water suitable for drinking. Many people pale with thought about the secondary use of sewage drain, but it is worth remembering that in nature in any case all the water performs a circulation. In fact, the corresponding doctor can provide water better qualityrather than received from rivers and lakes, not rarely taking crude sewage drains.
Main ways of water purification
Water clarification
The clarification is the water treatment stage, in the process of which the turbidity of water takes place by reducing the content of suspended mechanical impurities of natural and wastewater. The turbidity of natural water, especially surface sources in the flood period, can reach 2000-2500 mg / l (with the norm for the water and drinking destination - no more than 1,500 mg / l).
Lightening water by deposition of suspended substances. This feature is performed lighters, sumps and filtersrepresenting the most common water treatment facilities. One of the most widely used methods for reducing in water content of fine-disgraced impurities is their coagulation(Deposition in the form of special complexes - coagulants) with subsequent precipitation and filtration. After clarification, the water enters the tanks of pure water.
Water discolorationthose. The elimination or discoloration of various painted colloids or fully dissolved substances can be achieved by coagulation, the use of various oxidizing agents (chlorine and its derivatives, ozone, potassium permanganate) and sorbents (active coal, artificial resins).
Filtering with pre-coagulation filtering contributes to a significant decrease in the bacterial pollution of water. However, among those who remained after the water treatment, microorganisms may also be both pathogenic (bacillos of abdominal typhoids, tuberculosis and dysentery; vibrium cholera; polio viruses and encephalitis), which are a source of infectious diseases. For the final destruction of them, water intended for household purposes should be mandatory subjected to disinfection.
Disadvantages of coagulation, settling and filtering: costly and insufficiently effective water treatment methods, and therefore additional methods of quality improvement are required.)
Disinfection of water
Disinfection or disinfection is the final stage of the water treatment process. The goal is to suppress the vital activity of the pathoral microbes contained in the water. Since complete release, no upset, nor filtration, is given for the purpose of disinfection of water, chlorine and other methods described below are used.
In water treatment technology, a number of water disinfection techniques are known, which can be classified for five main groups: thermal; sorptionon active coal; chemical (with strong oxidizing agents); oligodynamia(exposure to the ions of noble metals); physical (With ultrasound, radioactive radiation, ultraviolet rays). The methods of the third group are most widely distributed from the listed methods. Chlorine, chlorine dioxide, ozone, iodine, mangartageous potassium are used as oxidizing agents; hydrogen peroxide, sodium and calcium hypochlorite. In turn, from the listed oxidants in practice give preference chlorine, chlorine lime, sodium hypochloride. The choice of the method of disinfection of water is carried out, guided by the flow rate and quality of the water being processed, the effectiveness of its preliminary cleaning, the terms of delivery, transport and storage of reagents, the possibility of automating processes and mechanization of labor-intensive work.
The water, which has passed the previous processing stages, coagulation, clarification and discoloration in a layer of a weighted sediment or upset, filtering, because there are no particles in the filtrate, on the surface or inside which there may be in the adsorbed state of bacteria and viruses, while remaining outside the effects of disinfecting agents.
Disinfection of water with strong oxidizing agents.
Currently, at the facilities of housing and communal services for water disinfection, as a rule, applied chlorination water. If you drink water from under the tap, you should know that it has chlororganic compounds, the number of which, after the procedure for disinfection of water, the chlorine reaches 300 μg / l. Moreover, this amount does not depend on the initial level of water pollution, these 300 substances are formed in water due to chlorination. Consumption of such drinking water can very seriously affect health. The fact is that the combination of organic substances with chlorine is formed trigalomethanes. These methane derivatives have a pronounced carcinogenic effect, which contributes to the formation of cancer cells. When boiling chlorinated water in it, the strongest poison dioxin is formed. Reduce the content of trigalomethane in water can be reduced by reducing the amount of chlorine used or replacing it with other disinfectants, for example, applying granulated activated carbon To remove the organic compounds generated during purification. And, of course, you need more detailed control over the quality of drinking water.
In cases of high turbidity and chromangery of natural waters, pre-chlorination of water is used, however, this method of disinfection, as described above, is not only not quite effective, but also harmful to our body.
Chlorination disadvantages: It is not sufficiently effective and at the same time brings irreversible harm to health, since the formation of trigalomethane carcinogens contributes to the formation of cancer cells, and dioxin - lead to the strongest poisoning of the body.
Disinfecting water without chlorine is economically impractical, since alternative methods of water disinfection (for example, disinfection ultraviolet radiation) sufficiently costly. An alternative chlorination was proposed by the method of disinfection of water with ozone.
Ozonization
A more modern procedure for disinfection of water is considered to be cleansing water with ozone. Really, ozonization Water at first glance is safer than chlorination, but also has its drawbacks. Ozone is very miserable and quickly destroyed, therefore its bactericidal action is short. But the water should still go through watering systemBefore finding out in our apartment. On this path, it will take a lot of trouble. After all, it is no secret that water pipes in Russian cities are extremely worn.
In addition, ozone also reaches the reaction with many substances in water, for example with phenol, and the products formed still toxic than chlorophenol. Ozonation of water turns out to be extremely dangerous in cases where bromine ions are present in the water at least in the most insignificant quantities, difficult even in laboratory conditions. When ozonation, poisonous compounds of bromine - bromides, dangerous to humans, even in micro-likes occur.
The water ozonization method has proven itself to process large masses of water - in pools, in collective use systems, i.e. Where need more careful disinfection of water. But it is necessary to remember that ozone, like the products of its interaction with the chlororanica is poisonous, therefore the presence of large concentrations of chlororanges at the water treatment stage can be extremely harmful and dangerous for the body.
Disadvantages of ozonation: Bactericidal action is short, in reaction with phenol still toxic than chlorophenol, which is more dangerous for the body than chlorination.
Disinfection of water by bactericidal rays.
CONCLUSIONS
All of the above methods are not enough effective, not always safe, and moreover, it is economically impossible: first - expensive and very expensive, requiring constant costs for maintenance and repair, secondly - with a limited service life, and thirdly - with high energy consumption .
New technologies and innovative methods for improving water quality
The introduction of new technologies and innovative methods of water treatment allows you to solve a complex of tasks providing:
Among the new technologies for improving water quality can be allocated:
Membrane Methods Based on modern technologies (including macroofiltration; microfiltration; ultrafiltration; nanofiltration; reverse osmosis). Used for desalination wastewater, solve the set of tasks of water purification, but purified water does not mean even that it is useful for health. Moreover, these methods are expensive and energy-consuming, which require constant service costs.
Current methods of water treatment. Activation (Structuring)liquids. Methods of activation of water today are known to date (for example, magnetic and electromagnetic waves; waves of ultrasonic frequencies; cavitation; impact of various minerals, resonant, etc.). The method of structuring fluid ensures the solution of a complex of water treatment tasks ( discoloration, softening, disinfection, degassing, water deferrizationetc.), at the same time eliminating chimspapers.
Water quality indicators depend on the methods of liquid structuring used and depend on the choice of technologies used, among which you can allocate:
- devices of magnetic water treatment;
- electromagnetic methods;
- cavitation water treatment method;
- resonant wave activation of water
(Contactless processing based on piezocrystals).
Hydromagnetic systems (HMS) Designed to process water in a stream by a constant magnetic field of a special spatial configuration (used to neutralize scale in heat exchanging equipment; for lightening water, for example, after chlorination). The principle of operation of the system is the magnetic interaction of metal ions present in water (magnetic resonance) and at the same time flowing process of chemical crystallization. The GMS is based on the cyclic effect on the water supplied to the heat exchangers with a magnetic field of a given configuration created by high-energy magnets. The method of magnetic treatment of water does not require any chemical reagents and therefore is environmentally friendly. But there are disadvantages. The HMS uses powerful permanent magnets based on rare earth elements. They retain their properties (magnetic field strength) for a very long time (dozens of years). However, if they are cut above 110 - 120 s, magnetic properties can relax. Therefore, HMS must be mounted where the water temperature does not exceed these values. That is, before its heating, on the line of the return.
Disadvantages of magnetic systems: The use of HMS is possible at a temperature not higher than 110 - 120 °FROM; insufficiently effective method; For complete cleaning, it is necessary to use in a complex with other methods, which is eventually inexpedient.
Cavitational water treatment method. Cavitation is an education in the liquid of cavities (cavitation bubbles or a cavity) filled with gas, steam or mixture thereof. Essence cavitation - Another phase state of water. In cavitation conditions, water moves from its natural state in steam. Cavitation occurs as a result of a local decrease in the pressure in the liquid, which can occur either with an increase in its velocity (hydrodynamic cavitation), or when the acoustic wave passes during the vacuum half period (acoustic cavitation). In addition, a sharp (sudden) disappearance of cavitation bubbles leads to the formation of hydraulic shocks and, as a result, to create a compression wave and stretching in a liquid with an ultrasonic frequency. The method will apply for cleaning from iron, stiffness salts and other elements exceeding the MPC, but is weakly effective when water disinfection. At the same time, it consumes consumes electricity, expensive in maintenance with consumable filtering elements (a resource from 500 to 6000 m 3 of water).
Disadvantages: consumes electricity, not effective and expensive in service.
CONCLUSIONS
The above methods are the most efficient and environmentally friendly comparison with traditional methods of water purification and water treatment. But have certain disadvantages: the complexity of installations, high cost, the need for consumables, maintenance difficulties, requires significant areas to install water purification systems; Insufficient efficiency, and besides this, restrictions on the use (temperature limit, stiffness, pH of water, etc.).
Methods of contactless activation of fluid (BOG). Resonant technologies.
Fluid processing is carried out contactlessly. One of the advantages of these methods is structuring (or activation) of liquid media, providing all of the above tasks to activate the natural properties of water without electricity consumption.
The most effective technology in this area is NORMAQUA technology ( resonant Wave Treatment Based on Piezocrystals), non-contact, environmentally friendly, without electricity consumption, not a magnetic, not served, the service life is at least 25 years. The technology is created on the basis of piezoceramic activators of liquid and gaseous media, which are inverter resonators emitting the waves of supermows intensity. As with the effects of electromagnetic and ultrasonic waves, unstable intermolecular bonds are torn under the influence of resonant oscillations, and water molecules are built into the natural natural physico-chemical structure into clusters.
The use of technology allows you to completely abandon chimbon preparation and expensive systems and water treatment consumables, and achieve an ideal balance between maintaining the highest quality water and cost savings to operate equipment.
Reduce water acidity (increase pH levels);
- save up to 30% of electricity on pumping pumps and disintegrate previously formed deposits of scale due to reducing the coefficient of water friction (increase in the time of capillary suction);
- change the redox water potential of EH;
- reduce overall rigidity;
- improve water quality: its biological activity, safety (disinfection up to 100%) and organoleptic.
Introduction
For many years and centuries, water treatment has not highlighted as a branch of technology and less - as a chemical technology industry. Empirically found techniques and water purification methods were used, mainly anti-infectious. And therefore, the history of water treatment is the history of devices for the preparation and purification of water of well-known chemical processes and technologies that have found or being used. Preparation of water for drinking and industrial water supply is fundamentally different from other areas of chemical technology: water treatment processes flow in large volumes of water and with very small amounts of dissolved substances. It means that large-sized equipment requires the devices of large equipment, and the small amount of substances extracted from water inevitably entails the use of "thin" methods of water treatment. Currently, the scientific foundations of water treatment technologies take into account the specified specifics of this industry are being enjoyed. And such work is far from completion, if you can talk about the final knowledge of water. It would be a huge exaggeration to argue that advanced scientific and design forces, the best engineering facilities were aimed at implementing the needs of water treatment. On the contrary, attention to this industry and, it became, funding was manifested in the smallest volume, according to the residual principle.
Tests that have fallen to the share of Russia over the past 12-15 years, to fully know and water treatment. And customers, and the supply of water preparatory equipment are more and more, if you can express it, individualized. In the past years, the supply was usually wholesale, and now, mostly - small-winding and solitary. Not to mention the fact that it was recently absent russian production Household filters and autonomous water supply systems, by definitions supplied in one or more copies. Yes, and the import of such equipment was very zubud. So, many people are involved in water treatment, earlier unfamiliar with it. In addition, many engineers who have been educated by other specialties are engaged in the small number of water treatment specialists in water. It is unlikely that you can call the easiest task of providing consumers with high-quality drinking water.
It is almost impossible to even briefly consider all the methods of water purification and water treatment. Here we wanted to draw readers to the most frequently used in practice in modern technologies on sewage treatment plants. various systems water supply.
1. Properties and water composition
Water is the most abnormal substance of nature. This commodity expression is due to the fact that the properties of water are in many respects do not comply with the physical laws, which are subject to other substances. First of all, it is necessary to recall: when we talk about natural water, all judgments should be attributed not to water as such, but to the aqueous solutions of different, in fact, the elements of the Earth. Until now, it is not possible to obtain chemically clean water.
1.1 Physical properties of water
The polar asymmetric structure of the water and a variety of its associates determine the amazing abnormal physical properties of water. Water reaches the greatest density at the plus temperature, it has anomalously high heat of evaporation and heat of melting, specific heat, boiling and freezing temperature. Big specific heat -4,1855 J / (g ° C) at 15 ° C - contributes to the temperature control of the temperature due to the slow heating and the cooling of the mass of water. In mercury, for example, the specific heat capacity at 20 ° C is only 0.1394 J / (g ° C). In general, the heat capacity of water is more than twice the heat capacity of any other chemical compound. This can explain the choice of water as a working fluid in the energy sector. Anomalous property of water - expansion of the volume by 10% when freezing provides ice swimming, that is, again retains life under the ice. Another extremely important property of water is extremely large surface tension . Molecules on the surface of the water are experiencing an intermolecular attraction on one side. Since the water of the forces of intermolecular interaction is abnormally large, each "floating" molecule on the surface of the water is drawn into the water layer. In the water, the surface tension is 72 mn / m at 25 ° C. In particular, this property explains the ball shape of water in conditions of weightlessness, water lifting water in the soil and in capillary vessels of trees, plants, etc.
Natural water - A complex dispersed system containing a variety of mineral and organic impurities.
Under the quality of natural water, the characteristic of its composition and properties is generally understood as a whole, which defines its suitability for specific types of water use, while quality criteria are signs of which water quality assessment is made.
1.2. Weighted impurities
Weighted solid impurities present in natural waters consist of clay particles, sand, yals, suspended organic and inorganic substances, plankton and various microorganisms. Weighted particles affect the transparency of water.
The content of weighted impurities, measured in mg / l, gives an idea of \u200b\u200bwater pollution by particles mainly with a conditional diameter of more than 1 · 10 - 4 mm. When the weighted substances containing suspended substances are less than 2-3 mg / l or more of the specified values, but the conditional diameter of the particles is less than 1 · 10-4 mm, the determination of water pollution is made indirectly on the turbidity of water.
1.3. Turbidity and transparency
Turbidity the water is caused by the presence of fine impurities due to insoluble or colloidal inorganic and organic substances of various origins. Along with turbidity, especially in cases where water has minor painting and turbidity, and their definition is difficult, while the joy « transparency» .
1.4. Smell
The nature and intensity of the smell natural water is determined by organoleptically. By the nature, odors are divided into two groups: natural origin (living and measuring organisms, driving plant residues, etc.); artificial origin (impurities of industrial and agricultural wastewater). Smells of the second group (artificial origin) are called the determining smell substances: chlorine, gasoline, etc.
1.5. Taste and taste
Distinguish four types of water flavors : Salty, bitter, sweet, sour. The qualitative characteristics of the shades of taste sensations - the taste - express descriptively: chlorine, fish, bitter and so on. The most common salty taste of water is most often due to the sodium chloride dissolved in water, the bitter - magnesium sulfate, sour - excessive carbon dioxide, etc.
1.6. Color
The water quality indicator that characterizes the intensity of the color of the water and the resulting content of painted compounds is expressed in the degrees of the platinum-cobalt scale and is determined by comparing the color of the test water with the standards. Color natural waters are due mainly to the presence of humus substances and compounds of trivalent iron, fluctuates from units to thousands of degrees.
1.7. Mineralization
Mineralization - the total content of all the water foundations found in the chemical analysis of water. Mineralization of natural waters, determining their specific electrical conductivity, varies widely. Most rivers have mineralization from several tens of milligrams in liter to several hundred. Their specific electrical conductivity varies from 30 to 1500 μS / cm. Mineralization of groundwater and salty lakes varies in the range from 40-50 mg / l to hundreds of g / l (the density in this case is already significantly different from the unit). The specific electronics of atmospheric precipitation with mineralization from 3 to 60 mg / l is 10-120 μm / cm values. Natural water is riserly separated into groups. The limit of freshwater is 1 g / kg - is established due to the fact that with the mineralization of more of this value, the taste of water is unpleasant - salty or bitter-salty.
1.8. Electrical conductivity
Electric conduct - This is the numerical expression of the ability of aqueous solution to carry out an electric current. The electrical conductivity of water depends mainly on the concentration of dissolved mineral salts and temperatures.
By the values \u200b\u200bof electrical conductivity, it is possible to approximately judge the mineralization of water.
Water type Mineralization density
1.9. Rigidity
Hardness of water it is determined by the presence of calcium, magnesium ions, strontium, barium, iron, manganese in water. But the total content in the natural waters of calcium and magnesium ions is incomparably more content of all other listed ions - and even their sums. Therefore, under the rigidity, the amount of calcium and magnesium ions is understood - the total rigidity that makes up from the values \u200b\u200bof the carbonate (temporary, disposable boiling) and non-comboonate (constant) stiffness. The first is caused by the presence of calcium and magnesium bicarbonates in water, the second presence of sulfates, chlorides, silicates, nitrates and phosphates of these metals. However, with the value of water rigidity, more than 9 mmol / l should be taken into account in water strontium and other alkaline earth metals.
According to ISO 6107-1-8: 1996, including more than 500 terms, stiffness is defined as the ability of water to form a foam with soap. In Russia, water rigidity is expressed in mmol / l. In rigid water, the usual sodium soap turns (in the presence of calcium ions) into an insoluble "calcium soap", forming useless flakes. And, while in this way, all the calcium hardness of water will not eliminate, the formation of foam will not begin. By 1 mmol / l of water stiffness for such a softening of water, 305 mg of soap is theoretically spent, almost - up to 530. But, of course, the main troubles - from the scale formation.
Stiffness classification (mmol / l): Water band Unit of measurement, mmol / l
Very soft .....................Do 1.5
Soft ............................1.5 - 4.0
Medium hardness ............ 4 - 8
Tough ........................ ... 8 - 12
Very tough ................... More than 12
1.10. Alkalinity
Alkalin water It is called the total concentration of the water-contained anions of weak acids and hydroxyl ions (expressed in mmol / l) reacting under laboratory studies with hydrochloric or sulfuric acids to form chloride or sulfur salts of alkaline and alkaline earth metals. The following water alkalinity forms are distinguished: bicarbonate (hydrocarbonate), carbonate, hydrate, phosphate, silicate, humate - depending on the anions of weak acids, which caused alkalinity.
The alkalinity of natural water, the pH of which is usually
Since in natural waters, almost always alkalinity is determined by bicarbonates, then for such water, the overall alkalinity is taken equal to carbonate rigidity.
1.11. Organic substances
Spectrum organic impuritiesvery wide:
Humic acids and their salts - sodium humats, potassium, ammonium;
Some impurities of industrial origin;
Part of amino acids and proteins;
Fulvocyuslotes (salt) and humic acids and their salts - calcium, magnesium, iron humats;
Fats of various origin;
Particles of various origin, including microorganisms.
The content of organic substances in water is estimated according to the methods for determining the oxidation of water, the content of organic carbon, the biochemical need for oxygen, as well as the absorption in the ultraviolet region. The value characterizing the content in water of organic and mineral substances oxidized by one of the strong chemical oxidants under certain conditions is called oxidation . There are several types of water oxidation: permanganate, bichromate, omnant, cerium (methods for determining the last two are rarely applied). Oxidability is expressed in milligrams of oxygen equivalent to the amount of reagent that went to the oxidation of organic substances contained in 1 liter of water. In the underground waters (artesian), organic impurities are practicing, and in the surface - "organicists" in a decisive degree more.
2. Choice of water treatment methods
Water treatment methods should be chosen when comparing the composition of the original water and its quality, regulated by regulatory documents or a water-defined water consumer. After the preliminary selection of water purification methods, the possibilities and conditions of their application are analyzed, outgoing from the task. Most often, the result is achieved by the phased implementation of several methods. Thus, important are both the choice of water treatment techniques and their sequence.
Water treatment methods are about 40. Only most frequently used are considered here.
2.1. Physical and chemical processes water treatment
These processes are characterized by the use of chemical reagents for destabilization and increasing the size of particles forming contamination after which the physical separation of solid particles from the liquid phase is carried out.
2.1.1. Coagulation and flocculation
Coagulation and flocculation are two completely different components of physico-chemical cleaning.
Coagulation - This is the stage, during which the colloidal particles are destabilized (similar to the balls with a diameter of less than 1 μm).
The word coagulation comes from the Latin "Coagulare", which means "agglomery, stick together, accumulate." When processing water, coagulation is achieved by adding chemical reagents to a water suspension, where scattered colloidal particles are assembled into large aggregates, called flakes or microchops.
Colloids are insoluble particles that are in a weighted water. Small sizes (less than 1 μm) make these particles extremely stable. Particles can be of different origin:
Mineral: IL, clay, silica, hydroxides and metal salts, etc.
Organic: Huminic and Fulvinic acids, dyes, surfactants and
Note: Microorganisms, such as bacteria, plankton, algae, viruses are also considered colloids.
Stability and, therefore, instability of suspended particles is a factor determined by different forces of attraction and repulsion:
Forces of intermolecular interaction
Electrostatic forces
Attraction of land
Forces participating in Brownian motion
Coagulation is both physical and chemical process. The reactions between particles and coagulant ensure the formation of aggregates and their subsequent deposition. Cationic coagulants neutralize the negative charge of colloids and form a loose mass, which is called microchops.
The coagulation mechanism can be reduced to two steps:
1- The neutralization of the charge: which corresponds to a decrease in electrical charges that repulse action on colloids.
2- The formation of particle aggregates.
Currently applied mainly mineral coagulants. They are based on, mainly salts were ironed aluminum. These are the most frequently used coagulants. The charge of the cation here is created by metal ions, which are formed from iron or aluminum hydroxides during contact with water. The main advantages of such coagulants are the versatility of their use and low cost.
Coagulation - This is an intermediate, but very important stage of the process of physico-chemical water treatment and wastewater. This is the first stage of removal of colloidal particles, the main function of which is to destabilize the particles. Destabilization mainly consists in neutralizing the electric charge present on the surface of the particle, which contributes to the sticking of colloids.
Flocculation - This is a stage, during which destabilized colloidal particles (or particles formed at the coagulation stage) are collected in the aggregates.
The flocculation step can only pass in water, where the particles are already destabilized. This is the stage, logically following coagulation. Flocculants with their charge and very high molecular weight (long monomer chains) fix the destabilized particles and combine them along the polymer chain. As a result, at the flocculation stage there is an increase in the size of the particles in the aqueous phase, which is expressed in the formation of flakes.
The links between destabilized particles and flocculant are usually ion and hydrogen.
2.2. Water clarification by filtration
The initial phase of water treatment, as a rule, is the release of it from suspended impurities - clarification of water, sometimes classified as pre-treatment.
There are multiple types of filtering:
- straining - the sizes of pores of the filter material are less than the sizes of detained particles;
- film filtration - under certain conditions after a certain initial period, the filter material is enveloped by film suspended substances, on which particles can be delayed even smaller than the pore size of the filtering material: colloids, minor bacteria, large viruses;
- volumetric filtration - suspended particles, passing through a layer of filter material, repeatedly change the direction and speed of movement in the slots between the granules and the fibers of the filter material; Thus, the filter duke can be quite large - more than with film filtration. Filtering in fabric, ceramic, almost all filters with nonwoven fibrous filtering elements are carried out in the first two - from the types named - types; In fine-grained bulk filters - according to the second type, in coarse-grained bulk - in the third.
2.2.1. Classification of filters with grainy loading
Grain filters are used mainly when cleaning liquids, in which the solid phase content is negligible, and the precipitate does not represent values, the main purpose of filters is for clarifying natural water. They are most widely used in water treatment techniques. Classification of filters for a number of basic signs:
♦ filtering speed:
Slow (0.1-0.3 m / h);
Speed \u200b\u200b(5-12 m / h);
Ultra-speed (36-100 m / h);
♦ the pressure under which they work:
Open or non-pat;
Pressure;
♦ number of filtering layers:
Single-layer;
Two-layer;
Multilayer.
Multilayer filters are most effective and economical, in which the loading is made up of materials with different density and particle size: on top of the layer - large light particles, downstairs are small heavy. With a downlink filtering direction, large contaminations are delayed in the upper layer of loading, and the remaining small - in the lower. Thus, the entire load is working. Lightening filters are effective when detaining particles size\u003e 10 microns.
2.2.2. Filtering technology
Water containing suspended particles, moving through a grain load, delaying suspended particles, brightened. The effectiveness of the process depends on the physicochemical properties of impurities, filtering loads and hydrodynamic factors. In the thickness of the loading, the contamination is accumulated, the free volume of the pores is reduced and the hydraulic load resistance increases, which leads to an increase in the pressure loss in the load.
IN generalThe filtering process can be consecrated to several stages: the transfer of particles from the flow of water to the surface of the filter material; fastening particles on beans and in the creams between them; The separation of fixed particles with the transition to them back into the flow of water. Extraction of impurities from water and fixing them on the loading grains occurs under the action of adhesion forces. The precipitate formed on the loading particles has a fragile structure that can be destroyed under the influence of hydrodynamic forces. Some of the previously sticking particles breaks away from the grains of loading in the form of small flakes and is transferred to subsequent loading layers (suffusion), where it is retained in pore channels. Thus, the process of water clarification should be considered as the total result of the adhesion and sufficient process. The clarification in each elementary layer of loading occurs until the intensity of the adhesion of the particles exceeds the intensity of the separation. As the upper load layers are satisfied, the filtering process goes to the following, the filtration zone is as if comes in the flow direction from the area where the filtering material is already saturated with pollution and the process of suffusion to the fresh download area prevails.
Then the moment occurs when the entire layer of loading the filter turns out to be saturated water pollution, and the required degree of water clarification is not provided. The suspension concentration at the load output begins to increase.
The time during which the clarification of water is achieved to a given degree called protective Time Loading . When it is achieved either when the limit pressure loss is reached, the clarifier filter must be translated into the explosion wash mode, when the load is washed with reverse current of water, and the contamination is discharged into drainage.
The possibility of detention by the coarse suspension filter depends mainly on its mass; Thin suspension and colloidal particles - from surface forces. The charge of suspended particles is important, since the colloidal particles of the charge of the same name cannot be combined into conglomerates, enlarged and settle: the charge prevents them closer. It overcomes this "alienation" of particles with artificial coagulation. As a result of coagulation, aggregates are formed - larger (secondary) particles consisting of accumulation of smaller (primary). As a rule, coagulation (sometimes, additionally, flocculation) is performed in sealing tanks.
Often, this process is combined with water softening with lime, or cost-to-wear, or eating softening. In conventional clarifying filters, a film filtering is often observed. Volumetric filtration is organized in two-layer filters and in the so-called contact clarifiers. The filter is covered with a lower layer of quartz sand with grain size of 0.65-0.75 mm and the upper anthracite layer with grain size of 1.0-1.25 mm. On the upper surface of the layer of large grains of anthracite, the film is not formed, suspended impurities penetrate the layer deep into the pores and are deposited on the surface of the grains. Weighted substances that have passed the anthracite layer are delayed by the lower layer of sand. When the filter is bleaching, the layers of sand and anthracite are not mixed, as anthracite density is twice as smaller than the density of quartz sand.
3. ion exchangelessimethods
Ion exchange - This is the process of extracting alone ions and replacing them with others. The process is carried out with the help of ion exchange substances - insoluble in water artificially granulated substances, special nonwoven materials or natural zeolites, having acidic or basic groups in their structure, capable of replacing positive or negative ions.
Ion exchange technology is the most applied today to softening and demineralizing water. This technology allows us to achieve water quality that meets the standards of different industrial and energy facilities.
The purification of the washing acidic water by the method of ionic exchanging is based on the ability of ion-insoluble ionites to enter into ion exchange with soluble salts, removing their cations or anions from solutions and eliminating the equivalent number of ions with which cationis and anionite is periodically saturated during regeneration.
The ion exchange method of water purification is used for desalting and purifying water from metal ions and other impurities. The essence of ion exchange lies in the ability of ion exchange materials to take the ion electrolyte solutions in exchange for an equivalent number of ion ions.
Water purification is carried out by ionites - synthetic ion exchange resins made in the form of granules with a size of 0.2 ... 2 mm. Jonites are made of polymeric substances from insoluble in water having a movable ion (cation or anion) on their surface, which under certain conditions enters into the exchange reaction with the ions of the same sign contained in water.
The selective absorption of the molecules of the solid adsorbent is due to the impact on them of unbalanced surface forces of the adsorbent.
Ion exchange resins have the ability to regenerate. After the depletion of the working exchange capacity of ionet, it loses the ability to exchange ions and it must be regenerated. Regeneration is made by saturated solutions, the choice of which depends on the type of ion exchange resin. Recovery processes, as a rule, flow in automatic mode. For regeneration usually spend about 2 hours, of which the explosion is 10-15 minutes, to filter the regenerating mortar - 25 - 40 minutes, for washing - 30 - 60 minutes. Ion exchange cleaning is implemented by sequential filtration of water through the cations and anions.
Depending on the type and concentration of impurities in the water, the required cleaning efficiency uses various schemes of ion exchange plants.
3.1. Cationis
Cationis As follows from the name, it is used to extract dissolved cations from water, i.e. cationis - the process of water treatment by the method of ion exchange, as a result of which the exchange of cations occurs. Depending on the type of ions (H + or Na +), which are in the volume of cationia, distinguish two main types of cation: sodium-cationing and hydrogen-cation.
3.1.1. Sodium-cationing
Sodium-cationic method It is used to soften water with a suspended substance in water not more than 8 mg / l and water color not more than 30 degrees. Water rigidity decreases with a single-stage sodium-cationing to the values \u200b\u200bof 0.05 - 0.1 mM-eq / l, with a two-stage - to 0.01 mG-eq / l. The sodium-cation process is described by the following exchange reactions:
The regeneration of Na-cation is achieved by filtration through it at a rate of 3-4 m / h of a 5-8% solution of the table salt.
The advantages of the table salt as a regeneration solution:
1. low cost;
2. availability;
3. Products regeneration lightly utilized.
3.1.2. Hydrogen-cationing
Hydrogen-cationic method Apply for deep softening of water. This method is based on filtering the treated water through a layer of cation containing hydrogen cations as exchange ions.
With hydrogen-cation of water, the pH of the filtrate is significantly reduced due to acids formed during the process. Carbon dioxide that is distinguished by softening reactions can be deleted with degarison. The regeneration of n-cation in this case is produced by 4-6% acid solution.
3.1.3. Other methods of cationing
Sodium chlorine ionics method it is used when it is necessary to reduce the total rigidity, the overall alkalinity and mineralization of the source water, increase the criterionpotential alkaline aggressiveness (reduce the relative alkalinity) of the boiler water, reduce carbon dioxide in a pair and the value of the steam boilers - by filtering alternately through a layer of sodium-cathilation by one filter and through the layers: first - Chlorine anion and then - sodium-cation in another filter.
Hydrogen-sodium cation (joint, parallel or consistent with normal or "hungry" regeneration of hydrogen-cationic filters) - to reduce overall rigidity, total alkalinity and mineralization of water, as well as an increase in the criterion for the potential alkali aggressiveness of boiler water, reduce the content of carbon dioxide in a pair and reduce the boiler purge.
Ammonium sodium-cation Used to achieve the same goals as in sodium-chlorine ionics.
3.2. Anionic
Anionic As follows from the name, it is applied to extract dissolved anions from water. Anionation is exposed to water that has already passed preliminary cation. The regeneration of anionite filter is usually carried out by alkali (NaOH). After the exhaustion of the working exchange capacity of the anion, it is regenerated to absorb the anions of the anions of strong acids are capable of both strongly and weakly-axis alion. Anions of weak acids - coal and silicon - are absorbed only by highly binding anionics for highly mineral anionics as a regenerant apply a solution of NaOH (therefore, the process is also called hydroxide-anionation). The mechanism of ion exchange and the influence of various factors on the technology of the anionic process is largely similar to their influence on the processes of cationation, but there are significant differences. Weakly-home anionics are in varying degrees are capable of sorption of different anions. As a rule, a certain series is observed, in which each previous ion is absorbed more actively and more than the next one.
In the technological chain of demineralization by ionization after hydrogen-cationic and weakly-axis, high-base anionic filters, if needed removed from the water of silicic acid anions and is sometimes an anions of coalic acid. The best results are obtained at low pH values \u200b\u200band almost complete decationation of water. The use of anionics in conditions of content in the original water of organic impurities has its own characteristics.
3.3. Water desalination by ionic method
To purify wastewater from anions of strong acids, the technological scheme of single-stage n-cation and on-anionation using strongly acidic cationia and a weakly-axis anion is used.
For deeper wastewater treatment, including salts, apply one or two-stage n-cationing on a strongly acidic cation with subsequent two-stage on-anionic on weakly, and then on highly binding anion.
When the content of a large amount of carbon dioxide and its salts, the tank of highly mining anion is rapidly deoxide and its salts occurs. To reduce exhaustion, wastewater after the coded filter is degassed in special degasters with a rashig rings nozzle or in other devices. If necessary, to ensure the value of pH ~ 6.7 and cleaning waste water from the anions of weak acids instead of the anionic filters of the second stage, a mixed action filter is used, loaded by a mixture of a strong acid cation and highly basic anion.
The desalting method of water by ion exchange is based on sequential water filtration through n-cationic, and then on-, NSO 3 -Ili CO 3 - anionic filter. The cations contained in water are exchanged to hydrogen-cations. In one-anionic filters, which passes water after n-cationic, anions formed acids exchange per ions. Requirements for water supplied on H-one filters:
weighted substances - no more than 8 mg / l;
sulfates and chlorides - up to 5 mg / l;
color - no more than 30 degrees;
oxidability permanganate - up to 7 mg O 2 / l;
iron general - no more than 0.5 mg / l;
petroleum products - the absence;
free active chlorine - no more than 1 mg / l.
If the starting water does not meet these requirements, it is necessary to pre-prepare water.
In accordance with the necessary depth of water desalination, one-, two- and three-step settings are design, but in all cases, strongly acidic H-cations with a large exchange ability are used to remove metal ions from water.
Single-stage ion exchange plants are used to obtain water with salt-containing to 1 mg / l (but not more than 20 mg / l).
In single-stage ionic installations, water is consistently passed through a group of filters with n-cation, and then through a group of filters with a weakly-axis anion; Free carbon oxide (CO 2) is removed in the degasser, installed after cationic or anionic filters, if they are regenerated by a solution of soda or hydrocarbonate. Each group should have at least two filters.
3.4. Water demineralization by ionovania
Water demineralization - A method designed to reduce water mineralization, including overall rigidity, general alkalinity, silicon compounds. The ion exchange method of separating water is based on sequential filtration of water through hydrogen-cationic, and then HCO 3 -, OH or CO 3 -Nonite filter. The filtrate forms an equivalent amount of acid from the anions, with which cations were associated. Formed in the process of decomposition of bicarbonates CO 2 is removed in decarbonizers.
In anionite filters (hydroxide-anionation) anions formed acids exchange to ions - (delayed by the filter). As a result, it turns out demineralized (desalted) water.
This method is actually "non-independent", synthetic. It represents a circuit number of variants of a combination of varying degrees of complexity - depending on the purpose of water treatment - hydrogen-cation and hydroxide-anionic.
3.5. Terms of application of ion exchange plants
In ion exchange settings, water containing salts must be supplied - up to 3 g / l, sulfates and chlorides - up to 5 mmol / l, suspended substances - no more than 8 mg / l, chromaticity - not higher than 30 degrees, permanganate oxidability - up to 7 MGO / l. In accordance with the necessary depth of water desalination, one-, two- and three-stage settings are designed, but in all cases, hydrogen hydrogen-cations are used to remove metal ions from water. For industrial and energy consumers, water can be prepared by a single-stage scheme - one cationic and one anionic filters; on a two-stage scheme - respectively, two codeditis and two anionic filters; According to the three-stage scheme, the third stage can be decorated in two options: separately cationic and anionite filters or alignment in one cation and anion filter.
After a single-stage scheme: water content - 2-10 mg / l; Specific electrical conductivity - 1-2 μS / cm; The content of silicon compounds does not change. Two-step circuit is used to obtain water with salt-containing 0.1-0.3 mg / l; Specific electrical conductivity of 0.2-0.8 μS / cm; The content of silicon compounds up to 0.1 mg / l. The three-stage scheme reduces the salt content to 0.05-0.1 mg / l; Specific electrical conductivity - up to 0.1-0.2 μS / cm; The concentration of silicic acid is to 0.05 mg / l. For household filters, single-stage demineralization is used - joint loading of the filter by cationis and anion.
3.6. Mixed action filters
Combining in one cation and anionite apparatus allows you to achieve a high degree of cleaning: almost all of the ions in the ion solution are extracted from the water. Purified water has a neutral reaction and low salt-containing. After being saturated with ions, a mixture of ionites - for regeneration - it is necessary to first divide on cationis and anion, having various density. The separation is carried out by the hydrodynamic method (the aqueous thread from the bottom up) or by filling the filter with a concentrated 18% solution of the reagent. Currently, the main foreign manufacturers are manufactured specially discovered by density and size sets of monodisperse resins granules, providing a high degree of separation and stability of indicators.
Due to the complexity of the separation operations of the mixture of cationia and anionitis and their regeneration, such devices are used mainly to clean the alleged waters and water purification, desolate before reverse osmosis, when regeneration is rarely conducted or ionites are applied once.
3.7. Features of ion exchange technology
It historically developed that almost all the designs of ion exchange filters are in parallel with accurate (straight-flow), that is, the cultivated water and the regenerating solution moves in the filter in one direction - from top to bottom. As the regeneration solution is promoted from top to bottom through the ionite layer, the concentration pressure is the difference of concentrations between the delayed ions (for example, calcium and magnesium) and the iones of the regenerating solution with the ions (for example, sodium) - it becomes less and less.
At the end of its path, the "weak" regeneration solution is found with a layer of ionet, containing some, although small, the number of ions that need to be out of ion. Displacement does not happen. As a result, the next flow of treated water does not reach the required quality.
This feature of the technology of ion exchange, as well as the properties of ionites, regenerants and lyotropic series, determine the fundamental disadvantages of the ion exchange technology of water purification: a large consumption of reagents, water for washing of ionite from the regeneration residue and a large amount of wastewater whose quality does not meet the requirements of regulatory documents.
The exit from the situation was found technologists offered two-stage - for sodium cationis and three-stage - for demineralizing ionics - filtering. A type of two-stage softening can be considered parallel-flow-counter-flow filtering: despite the name, in each of the filter pair, parallel filtering is carried out.
Decarbonization- removal of carbon oxide released in hydrogen-cation and anionic processes.
It is necessary to remove it from the water in front of highly axial anionic filters, as in the presence of CO 2 in water, part of the working exchange capacity of the anion is spent on the absorption of CO 2.
Traditionally, decarbonizers are used to remove carbon dioxide water - apparatus filled with various water distributors (more often - bulk, for example, rings of rashiga, pallee, etc.), called a nozzle, or without aggregates, and blurred by air towards the water flow. Depending on the scheme, the decarbonizer can be installed after the first, or the second stage of hydrogen-cation, or after the first (weakly-axis) stage of the anionation. The latter scheme is more often used in foreign developments. Spreads are obtained by ejector (vacuum, inkjet) devices. Their work is based on the creation of a high-speed flow in an ejector device, in which the flow vacuuming is occurring with the subsequent air supply to the water and its adduction. With small dimensions, such a design provides greater performance and high gase removal efficiency. In this case, free from 2. At small water treatment stations and with a small content in the initial water, the bicarbar of the NATOs use water preparation scheme without decarbonizers.
5. Barberacted water treatment methods
Water demineralization by ion exchange and thermal demineralization (distillation) allow the water to be cleaned, almost completely desalted it. However, the use of these methods revealed the presence of deficiencies: the need for regeneration, cumbersome and expensive equipment, expensive ionites, etc. In this connection, the rapid propagation was obtained by barrible water treatment methods.
The group of barrum methods includes reverse osmosis, microfiltration, ultrafiltration and nanofiltration. Reverse osmosis (pore sizes 1-15 Å The operating pressure of 0.5-8.0 MPa) is used to demineralizing water, and almost all ions are delayed by 92-99%, and with a two-stage system and up to 99.9%. Nanofiltration (pore sizes 10-70Å , Operating pressure 0.5-8.0 MPa) is used to separate the dyes, pesticides, herbicides, sucrose, some dissolved salts, organic substances, viruses, etc. Ultrafiltration (pore sizes 30-1000Å , Operating pressure 0.2-1.0 MPa) is used to separate some colloids (silicon, for example), viruses (including poliomyelitis), carbon soot, separation on milk fractions, etc. Microfiltration (pore sizes 500-20000Å , Operating pressure from 0.01 to 0.2 MPa) is used to separate some viruses and bacteria, fine pigments, dust of active coal, asbestos, dyes, separation of water-oil emulsions, etc. The larger pores are formed in the membrane, the more the filtering process through the membrane is understood, the more in the physical sense it is approaching the so-called mechanical filtration.
The intermediate group is formed by the so-called track membranes obtained by irradiation on the cyclotron of lavsanov (polyethylene terephtalant) films with a stream of heavy ions. After exposure to the film with ultraviolet rays and etching alkali in the film, pores with a diameter of 0.2-0.4 microns are formed (mainly 0.3 μm).
5.1. Reverse osmosis
Reverse osmosis - one of the most promising water treatment methods, the advantages of which are in small energy consumption, simplicity of designs of devices and installations, small dimensions and ease of operation; It is used to desalted water with pickling up to 40 g / l, and the boundaries of its use are constantly expanding.
The essence of the method. If the solvent and solution are divided by a semi-permeable partition that transmits only solvent molecules, then the solvent will start switch through the partition into the solution to those until the concentration of solutions on both sides membranes are not aligned. The process of spontaneous flow of substances through a semi-permeable membrane separating two solutions different concentrations (a special case - a pure solvent and solution), called osmosis (from Greek: osmos. - push, pressure). If you create a copigination over the solution, solvent transition rate through a membrane will decrease. When establishing an equilibrium, the pressure corresponding to it can serve as a quantitative characteristic of the reverse osmosis. It is called osmotic pressure and equally the pressure to be attached to the solution to lead it into equilibrium with a pure solvent separated from it by a semi-permeable partition. In relation to water treatment systems, where the solvent is water, the process of reverse osmosis can be represented as follows: if from the side of natural water flowing through the apparatus with some impurities apply a pressure exceeding osmotic, the water will leak through the membrane and accumulate on the other of her side, and impurities - remain with the starting water, their concentration will be increase.
In practice, the membrane usually do not have the perfect semi-perception and some transition through the dissolved membrane is observed.
Osmotic pressure solutions can reach tens of MPa. The working pressure in the reverse osmosis settings should be significantly larger, since their performance is determined by the driving force of the process - the difference between the working and osmotic pressure. Thus, at osmotic pressure of 2.45 MPa for sea water containing 3.5% salts, the working pressure in the desalination settings is recommended to maintain at 6,85-7.85 MPa.
5.2. Ultrafiltration
Ultrafiltration - The process of membrane separation, as well as fractionation and concentration of solutions. It occurs under the action of pressure difference (before and after the membrane) of solutions of high molecular weight and low molecular weight connections.
Ultrafiltration borrowed from reverse osmosis methods for obtaining membranes, as well as in many respects like it and hardware. The difference lies in much higher requirements for the removal from the membrane surface of the concentrated solution of a substance capable of forming in the case of ultrafiltration gel-like layers and poorly soluble precipitation. Ultrafiltration according to the process of maintaining the process and parameters - an intermediate link between filtering and reverse osmosis.
The technological possibilities of ultrafiltration in many cases are much wider than that of the reverse osmosis. So, with reverse osmosis, as a rule, there is a general detention of almost all particles. However, in practice, the problem of the selective separation of the components of the solution often occurs, that is, fractionation. The solution to this problem is very important because the separation and concentration of very valuable or rare substances (proteins, physiologically active substances, polysaccharides, complexes of rare metals, etc.) are possible. Ultrafiltration, in contrast to the reverse osmosis, is used to separate systems in which the molecular weight of the dissolved components is much larger than the molecular weight of the solvent. For example, for aqueous solutions, it is assumed that ultrafiltration is applicable when at least one of the components of the system has a molecular weight of 500 and more.
The driving force of ultrafiltration is the difference in pressures on both sides of the membrane. Usually ultrafiltration is carried out with relatively low pressures: 0.3-1 MPa. In the case of ultrafiltration, the role of external factors is significantly increased. So, depending on the conditions (pressure, temperature, the intensity of turbulization, the composition of the solvent, etc.), on the same membrane, one can achieve a complete separation of substances that is impossible with a different combination of parameters. Ultrafiltration restrictions include: a narrow technological range - the need to accurately maintain the process conditions; A relatively low concentration limit, which for hydrophilic substances usually does not exceed 20-35%, and for hydrophobic - 50-60%; Small (1-3 years) Membrane service due to sedimentation in the pores and on their surface. This leads to contamination, poisoning and impaired structure of membranes or deterioration of their mechanical properties.
5.3. Membranes
Determining when implementing membrane methods are the development and manufacture of semi-permeable membranes that meet the following basic requirements:
High separating ability (selectivity);
High specific performance (permeability);
Chemical resistance to the action of the components of the divided system;
The invariance of characteristics during operation;
Sufficient mechanical strength that meets the conditions of installation, transportation and
storage membranes;
Low cost.
Currently, there are membranes of two main types, made of acetylcellulose (mixture of mono-, di- and triacetate) and aromatic polyamides. The form of the membrane is divided into tubular, leafy (spirally rolled) and made in the form of hollow fibers. Modern reverse osmosis membranes - composite - consist of several layers. The total thickness is 10-150 μm, and the thickness of the layer determining the selectivity of the membrane, not more than 1 micron.
From a practical point of view, two indicators of the process are the greatest interest: the coefficient of detention of the dissolved substance (selectivity), and the performance (volumetric flow) through the membrane. Both of these indicators ambiguously characterize the semi-permeable properties of the membrane, since it is largely dependent on the process conditions (pressure, hydrodynamic situation, temperature, etc.).
6. Water Definition Methods
Water with a high content of iron has an unpleasant taste, and the use of such water in manufacturing processes (textile industry, paper production, etc.) is unacceptable, as it leads to the appearance of rusty spots and divorces on finished products. Iron and manganese ions contaminate ion exchange resins, so when you hold most of the ion exchange processes of the previous water treatment stage, they are removal. In thermal power equipment (steam and water-heating boilers, heat exchangers) iron is the source of the formation of iron-free deposits on the surfaces of heating. In water coming to the processing into barbecue, electrodialysis, magnetic devices - the iron content is always limited. Purification of water from iron compounds - in some cases a rather complicated task that can only be solved is comprehensive. This circumstance is primarily associated with the diversity of the forms of the existence of iron in natural waters. To determine the most effective and economical for specific water, the method of debitabilities, you need to test iron removal. The method of debiterating water, the calculated parameters and doses of reagents should be made based on the results of technological research performed directly at the source of water supply.
For imperificating surface water, only reagent methods are used, followed by filtration. Definition of groundwater is carried out by filtration in combination with one of the methods of pretreatment:
Simplified aeration;
Aeration on special devices;
Coagulation and clarification;
Introduction of such oxidant reagents like chlorine, sodium or calcium hypochlorite, ozone,
potassium permanganate.
With a motivated substantiation, cationing, dialysis, flotation, electrocoagulation and other methods are used.
To remove iron from water contained in the form of a colloid of iron hydroxide or in the form of colloidal organic compounds, such as iron humates, coagulation of aluminum sulfate or aluminum oxychloride, or iron vitrios with the addition of chlorine or sodium hypochlorite.
As filters for filters, sand, anthracite, sulfochegol, crumples, pyrolusitis, and filtering materials treated with a catalyst, accelerating the oxidation process of bivalent iron in trivalent, are used mainly. Recently, fillers with catalytic properties are becoming increasingly distribution.
If there is a colloid bivalent iron in the water, conducting trestle dearness . If there is no possibility to carry out it in the first stage of design, one of the above methods are chosen based on the test letta in the laboratory or the experience of similar installations.
7. Demanganation of water
Manganese is present in the earth's crust in large quantities and is usually found along with iron. The content of dissolved manganese in underground and surface waters, poor oxygen, reaches several mg / l. Russian sanitary standards limit the level of extremely permissible manganese content in the water and drinking water with a value of 0.1 mg / l.
In some European countries, the requirements are tougher: no more than 0.05 mg / l. If the manganese content is greater than these values, the organoleptic properties of water deteriorate. At manganese values, more than 0.1 mg / l appear spots on sanitation and technical products, as well as a unwanted taste of water. A precipitate is formed on the inner walls of the pipelines, which is peeled in the form of a black film.
In the underground waters, the manganese is in the form of well-soluble salts in a divalent state. To remove manganese from the water, it must be translated into an insoluble with the oxidation in three- and tetravalent shape. Oxidized forms of manganese are hydrolyzed with the formation of practically insoluble hydroxides.
For effective oxidation of manganese oxygen, it is necessary that the pH value of the purified water was at the level of 9.5-10.0. Permanganate potassium, chlorine or its derivatives (sodium hypochlorite), ozone makes it possible to conduct a demaganation process with smaller pH values \u200b\u200bof 8.0-8.5. For oxidation of 1 mg of dissolved manganese, 0.291 mg of oxygen is needed.
7.1. Demanganation methods
Deep aeration with subsequent filtration. At the first stage of water purification under vacuum remove free carbon dioxide, which contributes increase pH values \u200b\u200bup to 8.0-8.5. For this purpose use vacuum-ejection apparatus, when this in its ejection part occurs dispersion of water and its saturation of air oxygen. Next, water is sent to filtering through a grain load, for example, quartz sand. This cleaning method is applicable at permanent oxidation of the source water not more than 9.5 Mg / l. In the water required presence a bivalent iron, when the oxidation of which is formed by iron hydroxide, adsorbing Mn 2+ and catalytically its oxidizing.
The ratio of concentrations / should not be less than 7/1. If, in the original water, this ratio is not performed, then the sulfate of iron (iron vigor) is additionally metered.
Demanganization permanganate potassium. The method is applicable both for surface and groundwater. When entering potassium permanganate, dissolved manganese is oxidized with the formation of a poorly soluble manganese oxide. The precipitated manganese oxide in the form of flakes has a high developed specific one, which determines its high sorption properties. The precipitate is good catalyst that allows you to conduct demogenation when pH \u003d 8.5.
As already noted, potassium permanganate ensures removal from water not only manganese, but also iron in various forms. Smells are also removed and the taste quality of water is improved due to sorption properties.
After permanganate, potassium introduces a coagulant to remove oxidation and suspended products and further filtered on sand loading. When cleaning from manganese groundwater, in parallel with potassium permanganate, activated silicic acid or flocculants are introduced. This allows you to enlarge the flakes of manganese oxide.
8. Disinfection of water
Disinfection of water There are sanitary and technical measures to destroy bacteria and viruses in water that cause infectious diseases. There are chemical, or reagent, and physical, or non-reagent, ways to disinfect water. The most common chemical methods of water disinfection include chlorination and ozonation of water, to physical - disinfection of ultraviolet rays. Before disinfection, water is usually subjected to water purification at which helminth eggs and a significant part of microorganisms are removed.
With chemical methods of disinfection of water to achieve a persistent disinfection effect, it is necessary to properly determine the dose of the introduced reagent and ensure a sufficient duration of contact with water. The reagent dose is determined by trial disinfecting or calculated methods. To maintain the necessary effect in chemical methods of water disinfection, the reagent dose is calculated with an excess (residual chlorine, residual ozone), guaranteeing the destruction of microorganisms that fall into water for some time after disinfection.
In the existing practice of disinfection of drinking water chlorination Most common. In the US, 98.6% of water (overwhelming number) is subjected to chlorination. A similar picture takes place in Russia, and in other countries, i.e., in the world in 99 out of 100 cases for disinfection, either pure chlorine or chlorine-containing products are used
Such popularity of chlorination is also associated with the fact that this is the only way to ensure the microbiological safety of water at any point of the distribution network at any time due to the effect of the incense . This effect lies in the fact that after the implementation of the implementation of chlorine molecules into water ("Feature") the latter retain their activity relative to microbes and oppress their enzyme systems throughout the path of water on water networks from the water treatment facility (water intake) to each consumer. We emphasize that the effect of the afteraction is inherent in chlorine.
Ozonization based on the properties of ozone, decomposed in water to form atomic oxygen, destroying the enzyme systems of microbial cells and the oxidizing some compounds that give water an unpleasant smell (for example, humic bases). The amount of ozone needed to disinfect water depends on the degree of water pollution and is 1-6 mg / l upon contact in 8-15 minutes; The number of residual ozone should be not more than 0.3-0.5 mg / l, because Higher dose gives water a specific smell and causes corrosion water pipes. Due to the extensive energy consumption, the use of complex equipment and highly qualified technical supervision, ozonization has been applied to disinfection by indinted with centralized water supply of special purpose objects.
Of the physical ways to disinfect water, the greatest distribution received disinfection by ultraviolet rays The bactericidal properties of which are due to the effect on cellular exchange and especially for enzyme systems of the bacterial cell. Ultraviolet rays destroy not only vegetative, but also dispute shapes of bacteria and do not change the organoleptic properties of water. A prerequisite for the effectiveness of this method of disinfecting is the colorlessness and transparency of the disinfective water, disadvantage - the absence of a sequence. Therefore, the disinfection of water with ultraviolet rays is used mainly for underground and burrows. To disinfect the water of open water sources, the combination of ultraviolet rays with small doses of chlorine is used.
Of the physical ways of individual disinfection of water, the most common and reliable is boiling in which, besides the destruction of bacteria, viruses, bacteriophages, antibiotics, etc. biological factors, often contained in open water sources, are removed dissolved in water gases and the rigidity of water is reduced. The taste quality of water when boiling is changing little.
When controlling the efficiency of disinfection of water on water supply systems, the contents of saprophytic microflora and, in particular, intestinal sticks come from the content in disinfailed water, because All known pathogens of human infectious diseases that propagate water (cholera, abdominal typhoids, dysentery) are more sensitive to the bactericidal effect of chemical and physical means of water disinfection than the intestinal wand. Water is considered suitable for water use in 1 liter of no more than 3 intestinal chopsticks. At water supply stations using chlorination or ozonation, each 1 h (or 30 minutes) is checked the residual chlorine or ozone content as an indirect indicator of reliability of water disinfection.
In Russia, there was a serious position with the technical condition of water purifiers of centralized water intakes, which in many cases were designed and built 70-80 years ago. Their wear is increasing every year, and more than 40% of the equipment requires a complete replacement. An analysis of emergency situations shows that 57% of accidents at the facilities of VKC occur due to the windiness of the equipment, so its further operation will lead to a sharp increase in accidents, the damage from which will significantly exceed the costs of preventing them. The situation is aggravated by the fact that due to the wear of the networks, the water in them is subjected to secondary infection, and requires additional cleaning and disinfection. Even worse, the situation with centralized water supply in rural areas.
This gives grounds to name the problem of water hygiene, i.e., ensuring the population of benign reliably disgraced water, the most important problem requiring the integrated and most effective solution. Safe drinking water, to determine the management of drinking water quality published by the World Health Organization, should not be of no health risks as a result of its consumption throughout life, including various human vulnerability to diseases at different stages of life. The group of greatest risk in relation to the diseases transmitted through water includes children of infant and early age, people with weakened health or those who live in the unsanitary conditions and elderly people.
Everything technological schemes Purification and disinfection of water should be based on the main criteria for the quality of drinking water: drinking water should be safe in epidemiological terms, harmless to chemical composition and possess favorable organoleptic (taste) properties. These criteria are based on regulatory acts of all countries (in Russia SanPiN 2.14.1074-01). Stopped the main most frequently used disinfectants: chlorination, ozonation and ultraviolet disinfection of water.
8.1. Chlorination of water
In the last decade, there has been an increased interest in water treatment facilities in terms of lobbying corporate business interests. Moreover, these discussions are justified by good intentions to ensure the population of high-quality water. Under such arguments, the need for clean water consumption is attempted to introduce meaningless and unreasonable innovations in violation of tested technologies and SanPiN 2.14.1074-01, which meets the highest international standards and requires mandatory presence of chlorine in drinking water systems of centralized water supply (Remember the effect of the afternoon inherent in chlorine only). Therefore, it is time to dispel the delusions on which the health of the nation depends.
In addition to chlorine for disinfection, water is used to use its compounds from which sodium hypochlorite is more often used.
Sodium hypochlorite - Nacio. In industry, sodium hypochlorite is produced as various solutions with different concentrations. Its disinfecting effect is primarily based on the fact that when dissolved hypochlorite sodium just as chlorine, forms a chlorothy when dissolved in water. It has a direct disinfecting and oxidizing effect.
Different brands of hypochlorite are used in the following directions:
. the solution of the brand A according to GOST 11086-76 is used in the chemical industry to degrease drinking water and water for swimming pools, as well as for bleaching and disinfection;
. the brand B solution according to GOST 11086-76 is used in the vitamin industry, as an oxidizing agent for whitening tissues;
. the solution of the brand A according to the one is used to avoid the infection of waste and natural waters in the economic and drinking water supply. This solution is disinfected by the water of fisheries reservoirs, whitening agents are obtained and disinfection in the food industry;
. the brand B solution is used to disinfect territories that were contaminated with fecal discharges, household and food waste; It is also very good for disinfecting wastewater;
. the solution of the brand g, in according to the TU used for disinfection of water in the fishery reservoir;
. the solution of the brand E according to the TU is used for disinfection as well as in the brand and according to the one. It is also very common in catering facilities, in health care facilities, to disinfect wastewater, drinking water, whitening, on objects of go, etc.
Attention! Precautions: Sodium Hypochlorite Solution GOST 11086-76 Brand A is a very strong oxidizing agent, when it is capable of burning a burn, with a random hit in the eye - irreversible blindness.
When heated above 35 ° C, sodium hypochlorite decomposes with the subsequent formation of chlorates and chlorine and oxygen separation. PDC chlorine in the working area environment - 1 mg / MW; In the settlement environments: 0.1 mg / MW - the maximum one-time and 0.03 mg / MZ - daytime.
Sodium hypochlorite is not a combustible tool and is unprofitable. But, sodium hypochlorite in accordance with GOST 11086-76 brand A, when contacting organic combustible substance (sawdust, wood wood), during drying, is able to cause sudden self-burning.
Individual personnel protection should be carried out using overalls and individual means of protection: Gas mask brand b or BKF, rubber gloves and goggles protective.
When exposed to the solution of sodium hypochlorite on the skin and mucous membrane, urgently need to wash them under flowing stream of water for 20 minutes, when dropping a drop of the solution in the eyes, it is necessary to immediately rinse them with plenty of water and transport the victim to the doctor.
Storage of sodium hypochlorite. Sodium hypochlorite should be stored in a non-heated ventilated storage room. Do not allow storage with organic products, flammable material and acid. Do not allow sodium hydrochloride sodium salts and contact with such metals. This product is packaged and transported in a polyethylene container (container, barrel, canister) or titanium container and a tank container. The sodium hypochlorite product is not a stable and warranty storage period (Note to GOST 11086-76).
8.2. Ozonating water
Ozonating water It finds use when disinfecting drinking water, water swimming pools, wastewater, etc., allowing simultaneously to achieve discoloration, oxidation of iron and manganese, eliminate the taste and smell of water and disinfection due to the very high oxidizing ability of ozone.
Ozone - Blue or pale purple gas, which spontaneously dissociates in air and in aqueous solution, turning into oxygen. The ozone decay rate sharply exists in an alkaline medium and with increasing temperature. Has a large oxidative ability, destroys many organic substances present in natural and wastewater; poorly dissolved in water and quickly self-disperse; Being a powerful oxidizing agent, it may increase the corrosion of pipelines during prolonged exposure.
It is necessary to take into account some singing features. First of all, you need to remember the rapid destruction of ozone, that is, the absence of such a long-term action, like Chlorine.
Ozonation can cause (especially in high-color waters and waters with a large number of organics) the formation of additional precipitation, so it is necessary to provide for ozonizing the water filtration through active coal. As a result of ozonization, by-products are formed include: aldehydes, ketones, organic acids, bromates (in the presence of bromide), peroxides and other connections. When exposed to humic acids, where there is a phenolic-type aromatic compounds, phenol may appear. Some substances rack to ozone. This non-wealth is overcome by the introduction of hydrogen peroxide into water according to the technology of the company "Degron" (France) in a three-chamber reactor.
8.3. Ultraviolet water disinfection
Ultraviolet It is called electromagnetic radiation within the wavelengths from 10 to 400 nm.
For disinfection, the "neighbor area" is used: 200-400 nm (the wavelength of natural ultraviolet radiation at the surface of the Earth is greater than 290 nm). The highest bactericidal effect has electromagnetic radiation at a wavelength of 200-315 nm. In modern UV devices, radiation with a wavelength of 253.7 nm is used.
The bactericidal effect of ultraviolet rays is explained by the photochemical reactions occurring under their effects in the structure of the DNA molecule and RNA, which constitute the universal information base of the reproducibility of living organisms.
The result of these reaction is irreversible damage to DNA and RNA. In addition, the effect of ultraviolet radiation causes disorders in the structure of the membranes and cell walls of microorganisms. All this ultimately leads to their death.
The UV sterilizer is a metal housing, inside of which a bactericidal lamp is located. She, in turn, is placed in a protective quartz tube. Water ishes a quartz tube, processed by ultraviolet and, accordingly, disinfecting. In one installation there may be several lamps. The degree of inactivation or the proportion of microorganisms died under the influence of UV radiation is proportional to the intensity of radiation and exposure time. Accordingly, the number of neutralized (inactivated) microorganisms is exponentially growing with increasing radiation dose. Due to the different resistance of microorganisms, the dose of ultraviolet, necessary for inactivation, for example, 99.9%, varies greatly from small doses for bacteria to very large doses for disputes and the simplest. When passing through water, UV radiation weakens due to the effects of absorption and scattering. To account for this attenuation, the absorption coefficient is injected, the value of which depends on the quality of water, especially from the content of iron, manganese, phenol, as well as from turbidity of water.
turbidity - no more than 2 mg / l (transparency in font ≥30 degrees);
color - no more than 20 degrees of platinum-cobalt scale;
installations of UV); Kolya index - no more than 10,000 pcs / l.
For operational sanitary and technological control of the efficiency and reliability of water disinfecting with ultraviolet, as in chlorination and ozonation, the definition of the bacteria of the intestinal stick (BGPP) is used.
The experience of using ultraviolet shows: if the radiation dose setting is provided not lower than a certain value, then the steady effect of disinfection is guaranteed. In world practice, the minimum radiation dose requirement varies from 16 to 40 mJ / cm2. The minimum dose corresponding to Russian standards is 16 MJ / cm2.
The advantages of the method:
The least "artificial" - ultraviolet rays;
Universality and the effectiveness of the defeat of various microorganisms - UV rays
destroy not only vegetative, but also spore-forming bacteria that
chlorine chlorine retains vitality to the usual regulatory doses;
The physico-chemical composition of the treated water is preserved;
No restriction on the upper dose limit;
No need to organize a special security system, as in chlorination and
ozonation;
There are no secondary products;
No need to create a reagent economy;
The equipment works without special service personnel.
Method disadvantages:
Efficiency drop in the processing of poorly purified water (turbid, colored water is bad
shines);
Periodic washing of lamps from precipitation raids required when processing turbid and
rigid water;
There is no "Feature", that is, the possibility of secondary (after processing by radiation)
water infection.
8.4. Comparison of the main methods of water disinfection
The main methods of water disinfection, described above are the most diverse advantages and disadvantages set forth in numerous publications on this topic. Note the most weighty of them.
Each of the three technologies, if it is used in accordance with the norms, can provide the necessary degree of inactivation of bacteria, in particular, on the indicator bacteria of the intestinal stick group and the general microbial number.
In relation to the cysts of the pathogenic simplest, the high degree of cleaning does not provide any methods. To remove these microorganisms it is recommended to combine disinfection processes with processes reducing turbidity.
The technological simplicity of the chlorination process and the deficiency of chlorine determine the widespread dissemination of this method of disinfection.
The ozonization method is most technically complicated and expensive compared to chlorination and ultraviolet disinfection.
Ultraviolet radiation does not change the chemical composition of water even with doses, much more exceeding the practically necessary.
Chlorination can lead to the formation of unwanted chloroorganic compounds with high toxicity and carcinogenicity.
When ozoring, the formation of by-products, classified by standards as toxic - aldehydes, ketones and other aliphatic aromatic compounds is also possible.
Ultraviolet radiation kills microorganisms, but " the resulting fragments (cell walls of bacteria, fungi, protein fragments of viruses) remain in water. Therefore, subsequent fine filtering is recommended.
. Only chlorination Provides the effect of the afteraction, that is, it has a necessary long action, which makes the use of this method mandatory when submitting clean water into the plumbing network.
9. Electrochemical methods
Electrochemical methods are widely used when traditional methods of mechanical, biological and physico-chemical water treatment are not effective or cannot be used, for example, due to the deficit of production areas, the complexity of delivery and the use of reagents or for other reasons. Installations for implementing these methods are compact, high-performance, control and control processes are relatively simply automated. Usually, electrochemical processing is used in combination with other methods of cleaning, allowing you to successfully clean the natural water from impurities of various composition and dispersion.
Electrochemical methods can adjust the physicochemical properties of the treated water, they have a high bactericidal effect, greatly simplify the technological schemes of cleaning. In many cases, electrochemical methods exclude the secondary pollution of water anionic and cationic residues characteristic of reagent methods.
Electrochemical water purification is based on electrolysis, the essence of which is the use of electrical energy to conduct oxidation and recovery processes. The electrolysis process proceeds on the surface of the electrodes in the electrically conductive solution - electrolyte.
The electrolysis process is necessary: \u200b\u200ban electrolyte solution - contaminated water, in which ions are always present in one or another concentration that ensure the electrical conductivity of water; electrodes immersed in an electrolyte solution; External source of current; Currents - metal conductors connecting electrodes with a current source. The water itself is a bad conductor, but the charged ions in the solution are formed during the electrolyte dissociation, under the action of the voltage applied to the electrodes, move along two opposite directions: positive ions (cations) to the cathode, negative (anions) to the anode. Anions give the analogies their "extra" electrons, turning into neutral atoms. At the same time, the cations, reaching the cathode, is obtained from it the missing electrons and also become neutral atoms or a group of atoms (molecules). In this case, the number of electrons obtained by the anode is equal to the number of electrons transmitted by the cathode. A constant electric current flows in the chain. Thus, during electrolysis, redox processes occur: on the anode - the loss of electrons (oxidation), on the cathode - the purchase of electrons (recovery). However, the mechanism of electrochemical reactions is significantly different from conventional chemical transformations of substances. A distinctive feature of an electrochemical reaction - a proliferated separation of electrochemical reactions into two conjugate processes: the processes of decomposition of substances or new products occur at the border of the electrode solution using an electric current. When conducting electrolysis simultaneously with electrode reactions in the volume of the solution, a change in the pH and the redox potential of the system, as well as phase-dispersed transformations of water impurities occur, occur.
www. Aqua - Term. Ru
The readiness of heat stations and boiler houses by winter, in the framework of the All-Russian preparation program for the heating season, is raised. The need for work providing trouble-free operation of thermal equipment is on the fore. One of the main problems facing operational organizations is the formation of solid deposits on the inner surface of boilers, heat exchangers and pipelines of thermal stations. The formation of these sediments leads to serious energy losses. These losses can reach 60%. The growth of deposits significantly reduces heat transfer. Large sediments can fully block the operation of the system, lead to closure, accelerate corrosion and eventually disable expensive equipment.
All these problems arise due to the fact that for feeding thermal networks, as a rule, or absent for boiler plants, or those that are installed, morally and physically already outdated. Source water is often fed to the heating system without the necessary processing and preparation.
At the same time, the reliability and efficiency of the operation of the boiler house, the heat and energy and other similar equipment largely depends on the effectiveness of the water treatment. The extreme worniness of the equipment of many boiler rooms is often related to the fact that the latter was carried out very and for a long time.
How economically justified to spend money on water treatment?
Experts calculated that water treatment measures give fuel savings from 20 to 40%, the period of operation of boilers and boiler equipment is increased to 25-30 years, the costs of capital and current and current elements, boilers and thermal equipment are significantly reduced. The payback of water treatment plants depends on their performance and ranges from 6 months to 1.5 - 2 years.
A significant number of objects on which modern water treatment systems for various productivity and destination are installed, and the increased interest of operational services to this problem makes it possible to assert that people of which depend warm in our homes realized that the use of water treatment plants created on the basis of modern technologies and Constructive solutions - a pledge of reliable, uninterrupted, trouble-free work, both small boiler rooms and large power units.
Krasnov M.S., Ph.D., Engineer-technologist of the company "EKODAR"
It is not easy to use water into everyday life, using it can be called every minute. A person does not even notice how constantly, it wipes something, it washes, it erases. And does not erase, it prepares, or drink tea. It turns out that a person cannot exist without water resources. And it means that ways to bring water to the desired state should be given enough time.
A modern water treatment system implies water to bring to the necessary indicators, based on what cash impurities may include groundwater. Surface water is distinguished by the greatest amount of different types of inclusions. In general, both water may differ in such impurities:
All new and modern water treatment technologies Strictly subordinate to the types of impurities that can include water. Even different oil elements led to the creation, such cleaning elements such as fuel oil and fat trap. Identify in your water, harmful impurities can be in various indirect signs and here are some of them:
In fact, the types of impurities and their characteristics are much more. It is possible to guess about the presence of one or another impurity. But only a laboratory analysis will help to determine it. In such matters to your own opinion, it is impossible to rely, because Many impurities at the beginning can manifest themselves equally. It can confuse a person, and it will buy an irregular filter device that will not bring results.
This fact should summarize the consumer to the idea that a mandatory element of any new and modern water treatment will be a step of assessing the state of water. Many consumers using water from the central water supply systems are neglecting this stage. But in the first stage and strongly chlorinated and hard water Will behave equally. Therefore, there is a risk to confuse the type of impurities. Or you can always wait for the formation of a limescale and then to determine the device. True, the presence of rigidity in water does not at all exclude a high threshold of chloride. Analysis will cost the consumer no more than 2000 rubles. Therefore, is it worth risking the equipment and cleanliness of surfaces, expecting a precipitate forms?
In addition, you need to understand that you will have to choose from your financial opportunities. Perhaps it is worth a little more to wait with the installation of modern water treatment systems, but to podcap and mounted high-quality new system By year and decades.
An alternative to modern water treatment technologies are systems for cleansing surfaces from scale. In industrial realities, they have long lost the battle of progressive cleaning technologies. And the consumer still considers his funds and does not always have them enough for the treatment plants for all types of impurities.
Cleaning surfaces from new precipitation deposits should lead to positive results. But in fact it turns out that purified surfaces are only stimulated, accelerate the formation of a new fly. Clean the surface is not very difficult when it is rarely done. Worse, when this time-consuming process, which over the years you need to spend more often, and the result is worse every time.
The feature of the scale is that it settles on uneven surfaces, and it is much more complicated to eliminate it from such surfaces. She goes tightly. It is possible to eliminate it only significantly damaging the damage. Because of this, the equipment is faster. Moreover, it is possible to clean the scale with hydrochloric acid tools, can and metal brushes. The result will most likely, almost the same. Only there will be scratches on the surfaces, or dried by acid path. It is impossible to leave attention without attention. Any thickness lime bloom is a good heat insulator. Some half a million scale can completely output a powerful boiler!
As for other impurities, the fight against them does not cause doubts from the consumer, because Their at least can be seen or they can be felt, unlike rigidity in water. Yes, and consuming any water with other impurities, you can choose. Tough water can be consumed for years and do not feel harm. Significant, meaning. In every health, a negative trail, scale and rigidity leave slowly. Therefore, the manufacturers are aspires so today to promote softeners into mass consumption.
Choose some one but the perfect modern technology Water treatment is impossible today. It's simply no. All the same, to achieve a better result, you will have to use an integrated approach, which is influenced by the source parameters and the final, steamed with the financial capabilities of the consumer.
But, nevertheless, any kind of impurities today can be removed by physical impact or chemical reactions. The mansion is the membrane cleaning and softening technologies, and standard mechanical cleaning. The easiest way works mechanics. There is a backfilling or lattice with a different bandwidth. Dirty water, passing such obstacles, leaves the whole garbage to them almost, up to small grain. If there is also a sorbent in the composition of water treatment, then all the impurities are solid, even those that form the smell and turbidity of water are eliminated.
Rinse such a device simply, you only need to run water into the system in the opposite direction. Then the water simply will make the entire sediment on the grid. Or all that is stuck between grainsite particles or pebbles. So that the backfall is not covered with the calf, and did not finish the bacterial flare, it is treated with a special solution, it slows down the growth of bacteria. No additional expenses require.
The next option for water purification will be disinfection. You can eliminate harmful viruses using chemicals (any chlorine-containing elements will relate to reagent disinfection) or irradiation, for example, using an ultraviolet lamp. Small doses of its irradiation for the human body are absolutely harmless, and for most viruses are detrimental. To obtain drinking water in most cases, UV lamps are used, for the rest there are dispensers. But in this case, the products of their reactions have to be eliminated from the water. After all, besides bacteria, there are metal salts in water, for example. They can react with chemicals and form new substances that are again settled on the surfaces with a dense crust. UV technology in work is more economical, durable, but it does not have a residual effect, like the same chlorine. There is still chemical ozonation, but due to the fact that ozone is liquid oxygen, it is fortunately safe for a person. But for the equipment is not very. And it is necessary to produce ozone directly in place, which also adds difficulties.
Modern water treatment technologies for working with iron salts are aimed at turning the dissolved iron into a poorly soluble form, which can be easily filtered. In working either oxygen, as the strongest oxidizing agent, or manganese sand, which retains the salt of iron well. All the same principle of separation on reagents and not reagents. Today, non-deceive dearities are used to a greater extent. Because They are cheaper, although they consume electricity. The secret of UV technology is that air inside the water is chased under the influence of a powerful pump, forcing iron salts to oxidize and form a precipitate. It is not easy to fix it.
As for non-gential softeners, then the most convenient electromagnet is. It will help the water to make a softer. But it will help to get rid of unnecessary salts from old stocks. Any hostess will say how difficult it is to eliminate the old balances of scale. Especially when they settled inside the narrow passes and score them. It is necessary to disassemble everything, soak in acids and then try to disappear. With the unless water treatment technology, you do not have to do anything. Power lines will help new stiff salt salts to gradually disintegrate old residues, even in the most inconvenient places. And the equipment does not have to disassemble. Moreover, the magnet will work almost like a clock for several decades. Other devices cannot boast of such durability. Yes, and you constantly have to change something. And such a new genetic technology is extremely convenient for home consumption also with its blatant service. More precisely, you do not need to follow or change something. Screw to the pipe. Included in the outlet, and forgot about the device for about twenty years.
Moscow;
d.T.N. E.N. Bushyev, Professor,
k.T.N. ON THE. Eremin, associate professor,
FGBOVPO IGEU, Ivanovo
The water preparatory installation (VPU) on the TPP is designed to replenish the loss of the aqueous coolant in the main circuit. There are a large number of possible options for water treatment schemes for obtaining desalted water on TPP.
The greatest distribution in our country was the technology of chemical desalination based on direct-flow ionic filters. This technology has been applied for several decades and showed itself quite reliable for the water of small and medium mineralization (+<5 мг-экв/дм 3). Для вод с высокой минерализацией (+>5 MG-ECV / DM 3) or with an elevated content of organic compounds (OK\u003e 20 MGO / DM 3) use thermal desalting.
In natural water, the growth of pollution of technogenic organic compounds is constantly noted: fertilizers, pesticides, petroleum products, etc. Traditional chemical water treatment technologies remove these contamination is not effective enough, which leads to the formation of potentially acidic substances in the condensate-nutritional path, and, as a result, to numerous facts of violation of VIR.
The tightening of environmental requirements for wastewater water preparations, on the one hand, worsening the quality of the water being processed, on the other, the rise in price of reagents, ionites, as well as high operating costs led to the need to improve traditional technologies and the creation of new desalting schemes.
The most promising technologies for processing water low mineralization with an increased content of organic impurities, which is characteristic of the surface waters of the center and the North of Russia, are: countercurrent ionics and desalting based on membrane methods.
New VPUs based on countercurrent technologies are introduced at the Kalinin NPP, CHP-EVS-2 OJSC Severstal, etc. Currently accumulated the first experience of operating new installations, partially or fully equipped with imported equipment and filtering materials, not always taking into account the characteristics of impurities Natural waters, sometimes simplified in order to reduce capital costs.
The PPU with a nominal capacity of 1700 m 3 / h is in operation at the CHEP EVC-2 OJSC Severstal. Installation is designed to produce deeply softened water (JO<10 мкг-экв/дм 3) и включает две стадии обработки исходной (р. Шексна) воды: осветление на механических однокамерных фильтрах (12 шт. с единичной производительностью 145 м 3 /ч) с периодическим подключением контактной коагуляции и Na-катионирование на противоточных фильтрах (4 шт. с единичной производительностью 585 м 3 /ч).
The countercurrent Na-cationic filter involves filtering the clarified water from the bottom up with a flow rate of 170 to 585 m 3 / h. The filter is a two-chamber apparatus (D \u003d 3.8 m) with three "false bottom" type drainage devices and a thousand cap elements in each device, overlapping the entire cross-section of the filter. The filter is loaded with C-100 cationite (ionet volume - 30 m 3: 10 - bottom and 20 - from above) with a floating layer of inert.
According to the results of laboratory studies and industrial tests, it was found that this cation is steadily working with the working exchange capacity of EP \u003d 1200 ÷ 1400 Mr. 3 at a specific consumption of salt on the regeneration of 100 g / g of eq. When loading in the range of 170 ÷ 500 m 3 / h per filter (filtering rate up to 50 m / h, diameter 3.8 m), the stiffness of the softened water is kept at 2 μg-eq / dm 3. The first filtercycles amounted to 25,000 m 3, a year later, the filterbile decreased to 18,000-20000 m 3.
The high quality of the sensitive water with a large single performance of ionic filters is provided by the deep automation of control, both separate filters and the entire installation as a whole. Installation can work and operates in fully automatic mode. At the same time, the operational staff controls the status of the process on computer screening forms of visualization and at any time can switch the control of the installation to manual mode.
This installation worked under the control of employees of the HCTE IHEU Chair almost a year mostly in automatic mode. The production of softened water for the filtercycle was 20000 m 3, against 6000-8000 m 3 on traditional straight-flow filters in equal conditions. Specific waste costs are reduced by 20%, water consumption on its own needs of the NA-cationic filter was 1% compared with 35% of traditional technology.
Experience of operation of counter-flow technologies proves their advantages compared to traditional: reducing the number of necessary water preparation equipment; High exchange tanks of ionets; The high quality of the filtrate, which is provided with small expenditures of regeneration reagents - 1.8-2.2 Mr. / eq / Mr.; Reducing the number of highly mineralized wastewater.
However, due to the lack of a second (barrier) stage and the difficulty of determining the time of the output on the regeneration, the disabling of the countercurrent filter is often carried out by the number of passed water with a significant reserve, which leads to the non-scope of desalted water. In countercurrent regeneration, the intensity of regeneration increases and, as a result, the number of switchings, which requires a high culture of maintenance of such installations, reliable fittings, automation and control tools. All of them require the use of clarified water, deeply purified from suspended, organic substances, as well as iron compounds. The effectiveness of the countercurrent is the higher, the higher the quality that comes to filters water.
Recently, much attention is paid to malformed methods and primarily membrane technologies.
Some new VPUs are based on the use of reverse osmosis for water demineralization using traditional technologies (clarifier, mechanical filters). Examples are such a VPU, the CHP of OJSC Severstal, (Fig. 1). The use of reverse osmosis makes it possible to extract at one level of cleaning to 96-98% of salts, which is close to the effectiveness of one stage of ion exchange.
The permeate fingering system may consist of a level of ion exchange with separate N- and on-ionics (direct-flow or countercurrent), and (or) with a mixed action filter. Since there is partially desalted water to such an installation, the filter resource is significant and reaches tens and hundreds of thousands of cubic meters.
A comparison of the economic efficiency of water desalination with ion exchange and reverse osmosis has shown that during the content of more than 150-300 mg / l reverse osmosis more efficiently even countercurrent ionics.
The existing operating experience of reverse osmosis installations (WEU) suggests that the main factor on which the work of membranes depends is the observance of the quality of water supplied for processing. Manufacturers of membranes for nutrient water, which runs on the Hyo, presented the requirements presented in Table. one .
Table 1. Requirements for water coming on the WEU.
Analysis of these requirements shows that there are no restrictions on the content of salts contained in surface water sources, to work in a wide range of pH indicator. It is limited only to the content of those substances that can lead to poisoning or scoring membranes. Traditional water treatment indicators of water lightening quality (concentration of suspended substances, turbidity according to the "cross", transparency, chromaticity, oxidation) do not give an adequate understanding of the relationship between the productivity of membranes and the contamination of their surface and the pores of suspended and colloidal particles. Firms manufacturers of reverse osmosis elements estimate the quality of the water being processed, primarily indicator of SDI. Maximum permissible SDI - 5, and with SDI values \u200b\u200bfrom 3 to 5, manufacturers include water to be problematic, steady operation of the reverse osmosis element is guaranteed at SDI<3.
However, experience shows that in schemes with traditional technology of prevailing, the quality of water coming into the WEA often does not meet the requirements for the content of iron and oxidation. The required quality of such water can be achieved by the use of ultrafiltration at the pre-first stage (Fig. 2).
Ultrafiltration (UV) allows not only to obtain water, practically free from mechanical impurities, but also together with coagulation to remove a significant amount of organic matter (up to 60% of the initial number), as well as silicic acid. As an example, it is possible to obtain the results of the installation of ultrafiltration on (water supply source - the court river) (Table 2).
Table 2. The results of the installation of UV.
The introduction of UV at the previation stage significantly increased the productivity of reverse osmosis membranes, several times shorten the frequency of chemical flushing, released production areas, reduced the consumption of coagulant, provided the ability to refuse to lime.
The joint use of ultrafiltration and reverse osmosis makes it possible to create a unauthorized water treatment system to obtain a filtrate with electrical conductivity at 1-5 μm / cm. In such schemes, further allowing water quality to regulatory values \u200b\u200bis usually ion exchange (Fig. 2) by the method.
The reliability of the combined membrane-terminal installation (Fig. 2) is large, since even with possible disorders of the reverse osmosis system, the doctrine node will provide a given water quality. At the same time, the need for acid and alkali is maintained, so this technology, although to a lesser extent, has the same disadvantages as traditional. Such a technology is applied on, etc.
The main disadvantage of all membrane systems is a fairly low utilization of the source water. If in a traditional ion exchange scheme with coagulation and mechanical filtering, its own needs is 10-20%, then for a typical combination of ultrafiltration and reverse osmosis, this indicator is 40-50%. However, it should be borne in mind that concentrates from ultrafiltration installations and reverse osmosis on salt-containing are often within the limits of normalized values \u200b\u200band can be unorded.
Combined membrane-ion exchange schemes having a high degree of economic efficiency and reliability are the optimal and recommended method in the reconstruction of existing VPUs, where ion exchange filters, reagent and waste management and neutralization systems are already available. The amount of concentrated wastewater and the reagent consumption in this case are tens of times less than with a purely ion exchange scheme. The obtained wastewater can be diluted to permissible norms of the concentrate of membrane installations.
From the point of view of ensuring the minimum consumption of reagents and the highest environmentally friendliness with high quality of desalted water, complex PPUs consisting exclusively of membrane modules of various purposes: ultra- and nanofiltration, reverse osmosis, membrane degassing and electrodeionization, called generally - integrated membrane technologies ( BMI).
In a complex membrane installation (Fig. 3), water is consistent on the electrodeionization unit. Electroeonization (EDI, EDI) is a process of continuous desalination of water using ion exchange resins, ion-selective membranes and a constant electric field.
With the degree of use of the source water, 90-95% purified water has a specific electrical conductivity of 0.1 μs / cm (Table 3), as well as minimal silicone and general organic carbon. In this case, the concentrate pickling is usually lower than the salt-containing of the water supplied to the installation of the reverse osmosis, so it all returns to the input of this installation to reuse.
Table 3. Characteristics of electrocyonization installations.
All manufacturers of electrodeionization installations make very high requirements for water supplied to the EDI installation, regardless of its design (Table 4).
Table 4. Typical manufacturers' requirements for EDI installations.
To increase the reliability of the complex membrane water treatment systems on the basis of BMI, use at the pre-desalination stage of two-stage reverse osmosis. In this case, the quality of water supplying the installation of electrodeionization, knowingly above the requirements of manufacturers and any violations in the operation of reverse osmosis settings become non-critical. With the deterioration of the performance of the first stage (naturally in acceptable limits), the specified quality is guaranteed to provide the second stage.
Complex membrane installation for preparing deep desalted water, made in accordance with this scheme, provides a minimum amount of waste. There is no need for acid-alkaline farm, operational costs are reduced and environmental parameters are dramatically improved.
Such installations are most appropriate for newly under construction facilities. This is especially true for hard-to-reach areas, where the supply of reagents is difficult. Complex membrane installation is successfully operated on.
The general element in all considered desalting schemes based on membrane methods is the installation of reverse osmosis. When exploiting water preparation installation, performance is constantly changing. Often there is a significant decrease in performance associated with the suspension of the heat and power equipment or termination of the production pair of the consumer, which leads to the problem of ensuring the minimum flow of the treated water through the WEU.
With incomplete loading of the main equipment of PSU-325 blocks, the need for desalted water is reduced. This causes incomplete loading of the UOO. Initially, 2 parallel workers (Fig. 4, a) were designed on Ivsk. During the idle of one of the WEU, it is either placed on preservation, or the water circulation is made daily on the Haws to prevent the occurrence of deposits. This leads to additional losses and an increase in the cost of desalted water.
Since the reagents used to preserve the WSO have a sufficiently high cost, and it is possible to periodically connect the second installation of the reverse osmosis, then when working one of the blocks, conservation is an inefficient event.
To prevent losses, savings of chemical reagents for the FSD regeneration, measures were provided to reduce additional losses in simple equipment: the sequential inclusion of Woo 1 and Woo 2 to work (Fig. 4, b). Each installation includes 4 housings, also operating on a two-stage diagram (Fig. 5).
With a consistent turn on the reverse osmosis settings (Fig. 4), the permeate with the Woo 2, operating as the I stage, is supplied to the WEU 1 (II stage). At the same time, the concentrate with the WEU 2 is reset into the sewage system, and with the UPO 1 is mixed with the source water supplied to the I stage.
The starting water is supplied to the installation of the reverse osmosis on the housing of the AO1-AO3 (Fig. 5), then the permeate is fed to the FSD, and the concentrate is fed to AO4, where it is also divided into permat and concentrate. Permeate is fed to the FSD, and the concentrate is reset into the sewer.
After preliminary calculations in February 2012, industrial tests of the work of Woo 1 and Woo 2 were carried out in series. The results of the calculations are shown in Table. 5, in fig. 6 shows the test results.
| Indicator | Loving + coagulation Iron sulfate | Coagulation
sulfat aluminum |
|
| when turning on the Hoo in one step | when turning on the Hoo in two steps | ||
| Installation performance, m 3 / h | 18 | 18 | 18 |
| Total watch consumption of water coming on Woo, m 3 / h | 22,06 | 21,96 | 21,96 |
| Lighter capacity VTI-100, m 3 / h | 30,2 | 28,65 | 30,03 |
| FSD filtering, m 3 | 21240 | 63720 | 63720 |
| Acid consumption for regeneration, t / year | 0,54 | 0,16 | 0,16 |
| Alkali consumption for regeneration, t / year | 0,54 | 0,16 | 0,16 |
The data obtained proves improving the quality of desalted water after the second stage of processing on the WEU. The content of sodium ions, silicic acid and electrical conductivity is reduced by more than 3 times, the content of iron and chloride compounds is also reduced.
Tracking the dynamics of changes in the quality of desalted water, it can be noted that the two-stage desalination on the uho does not allow to reduce the value of electrical conductivity, however, it allows to obtain the required water quality parameters for the content of compounds of silician and sodium compounds for additive water boiler-utilizers. Improving the quality of the source water for the FSD allows you to reduce the ionic load on them more than 3 times, which leads to a significant increase in the filtercycle, a decrease in the amount of water used on the own needs of VPU, reduce the need for acid and alkali for regeneration. Therefore, the environmental damage caused by the environment is reduced.
Tests with coagulant - aluminum sulfate With a two-stage scheme of operation of reverse osmosis installations showed that it is possible to improve the quality of water going on the WEU, and increase the resource of the cartridge filtering elements for the WEU.
Thus, a large number of new water preparation equipment with high environmental characteristics appeared on the domestic energy market. The absence of a regulatory framework for their use and controversial operation of the headquarters on the domestic TPP, especially for waters with an increased content of organic substances, is prevented in widespread their production.
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